Showing papers in "Applied and Environmental Microbiology in 1983"
TL;DR: With this methodology, previously undetected large plasmids were observed and a scaled-down protocol is very useful for rapidly screening the plasmid content of streptococcal strains.
Abstract: A procedure for the rapid isolation of plasmid DNA larger than 30 megadaltons from lactic streptococci is described This protocol can be used on a preparative scale to isolate sufficient quantities of plasmid DNA required for restriction analysis, cloning, or transformation experiments A scaled-down protocol is very useful for rapidly screening the plasmid content of streptococcal strains With this methodology, previously undetected large plasmids were observed
1,076 citations
TL;DR: It was determined that multiple-antibiotic-resistant E. coli organisms exist in large numbers within the major reservoirs of enteric diseases for humans while existing in comparatively low numbers elsewhere.
Abstract: Escherichia coli isolates taken from environments considered to have low and high enteric disease potential for humans were screened against 12 antibiotics to determine the prevalence of multiple antibiotic resistance among the isolates of these environments. It was determined that multiple-antibiotic-resistant E. coli organisms exist in large numbers within the major reservoirs of enteric diseases for humans while existing in comparatively low numbers elsewhere. These differences provide a method for distinguishing high-risk contamination of foods by indexing the frequency with which multiple-antibiotic-resistant E. coli organisms occur among isolates taken from a sample.
1,041 citations
TL;DR: The number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species.
Abstract: The adhesion of five strains of bacteria, i.e., Staphylococcus aureus (strain 049), Staphylococcus epidermidis (strain 047), Escherichia coli (strains 055 and 2627), and Listeria monocytogenes, to various polymeric surfaces was studied. The design of the experimental protocol was dictated by thermodynamic considerations. From the thermodynamic model for the adhesion of small particles from a suspension onto a solid substratum, it follows that the extent of adhesion is determined by the surface properties of all three phases involved, i.e., the surface tensions of the adhering particles, of the substrate, and of the suspending liquid medium. In essence, adhesion is more extensive to hydrophilic substrata (i.e., substrata of relatively high surface tension) than to hydrophobic substrata, when the surface tension of the bacteria is larger than that of the suspending medium. When the surface tension of the suspending liquid is larger than that of the bacteria, the opposite pattern of behavior prevails. Suspensions of bacteria at a concentration of 10(8) microorganisms per ml were brought into contact with several polymeric surfaces (Teflon, polyethylene, polystyrene, and acetal and sulfonated polystyrene) for 30 min at 20 degrees C. After rinsing, the number of bacteria adhering per unit surface area was determined by image analysis. The surface tension of the suspending medium. Hanks balanced salt solution, was modified through the addition of various amounts of dimethyl sulfoxide. It was found that the number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species. The surface tensions of the bacteria obtained in this fashion are in excellent agreement with those obtained by other methods.
721 citations
TL;DR: Strains of Vibrio cholerae, both O1 and non-O1 serovars, were found to attach to the surfaces of live copepods maintained in natural water samples collected from the Chesapeake Bay and Bangladesh environs, which revealed that the oral region and egg sac were the most heavily colonized areas of the copepod.
Abstract: Strains of Vibrio cholerae, both O1 and non-O1 serovars, were found to attach to the surfaces of live copepods maintained in natural water samples collected from the Chesapeake Bay and Bangladesh environs. The specificity of attachment of V. cholerae to live copepods was confirmed by scanning electron microscopy, which revealed that the oral region and egg sac were the most heavily colonized areas of the copepods. In addition, survival of V. cholerae in water was extended in the presence of live copepods. Attachment of viable V. cholerae cells to copepods killed by exposure to -60 degrees C was not observed. Furthermore, survival of V. cholerae was not as long in the presence of dead copepods as in the live copepod system. A strain of Vibrio parahaemolyticus was also seen to attach to copepod surfaces without effect on survival of the organism in water. The attachment of vibrios to copepods was concluded to be significant since strains of other bacteria, including Pseudomonas sp. and Escherichia coli, did not adhere to live or dead copepods. Attachment of V. cholerae to live copepods is suggested to be an important factor of the ecology of this species in the aquatic environment, as well as in the epidemiology of cholera, for which V. cholerae serovar O1 is the causative agent.
679 citations
TL;DR: Examination of strains of L. acidophilus within the six homology groupings of Johnson et al. demonstrated that production of the bacteriocin lactacin B could not be used in classification of neotype L. Acidophilus strains, however, the usefulness of employing sensitivity to lactac in B in classified of dairy lactobacilli is suggested.
Abstract: A total of 52 strains of Lactobacillus acidophilus were examined for production of bacteriocins. A majority (63%) demonstrated inhibitory activity against all members of a four-species grouping of Lactobacillus leichmannii, Lactobacillus bulgaricus, Lactobacillus helveticus, and Lactobacillus lactis. Four L. acidophilus strains with this activity also inhibited Streptococcus faecalis and Lactobacillus fermentum, suggesting a second system of antagonism. Under conditions eliminating the effects of organic acids and hydrogen peroxide, no inhibition of other gram-positive or -negative genera was demonstrated by L. acidophilus. The agent produced by L. acidophilus N2 and responsible for inhibition of L. leichmannii, L. bulgaricus, L. helveticus, and L. lactis was investigated. Ultrafiltration studies indicated a molecular weight of approximately 100,000 for the crude inhibitor. The agent was sensitive to proteolytic enzymes and retained full activity after 60 min at 100 degrees C (pH 5). Activity against sensitive cells was bactericidal but not bacteriolytic. These characteristics identified the inhibitory agent as a bacteriocin, designated lactacin B. Examination of strains of L. acidophilus within the six homology groupings of Johnson et al. (Int. J. Syst. Bacteriol. 30:53-68, 1980) demonstrated that production of the bacteriocin lactacin B could not be used in classification of neotype L. acidophilus strains. However, the usefulness of employing sensitivity to lactacin B in classification of dairy lactobacilli is suggested. Images
609 citations
TL;DR: The demonstration that sulfate reducers can successfully compete with methanogens for hydrogen and acetate in sediments at in situ sulfate concentrations of 60 to 105 muM extends the known range of sediment habitats in which sulfate reduction can be a dominant terminal process.
Abstract: Acetate and hydrogen metabolism by sulfate reducers and methanogens in the profundal sediments of an oligotrophic lake were examined. Inhibition of sulfate reduction with molybdate stimulated methane production from both hydrogen and acetate. Molybdate did not stimulate methane production in sediments that were preincubated to deplete the sulfate pool. Sulfate reduction accounted for 30 to 81% of the total of terminal metabolism proceeding through sulfate reduction and methane production in Eckman grab samples of surface sediments. The ability of sulfate reducers to effectively compete with methanogens for acetate was related to the sulfate reducers' lower half-saturation constant for acetate metabolism at in situ sulfate concentrations. Processes other than sulfate reduction and methanogenesis consumed hydrogen at elevated hydrogen partial pressures and prevented a kinetic analysis of hydrogen uptake by sulfate reducers and methanogens. The demonstration that sulfate reducers can successfully compete with methanogens for hydrogen and acetate in sediments at in situ sulfate concentrations of 60 to 105 μM extends the known range of sediment habitats in which sulfate reduction can be a dominant terminal process.
524 citations
TL;DR: Results suggest that the ligninolytic degradation activity of the fungus was responsible for the decolorization of these polymeric dyes.
Abstract: The polymeric dyes Poly B-411, Poly R-481, and Poly Y-606 were examined as possible alternatives to the radiolabeled lignin previously used as a substrate in lignin biodegradation assays Like lignin degradation, the decolorization of these dyes by the white rot basidiomycete Phanerochaete chrysosporium occurred during secondary metabolism, was suppressed in cultures grown in the presence of high levels of nitrogen, and was strongly dependent on the oxygen concentration in the cultures A variety of inhibitors of lignin degradation, including thiourea, azide, and 4′-O-methylisoeugenol, also inhibited dye decolorization A pleiotropic mutant of P chrysosporium, 104-2, lacking phenol oxidase and ligninolytic activity was also not able to decolorize the polymeric dyes, whereas a phenotypic revertant strain, 424-2, regained this capacity All of these results suggest that the ligninolytic degradation activity of the fungus was responsible for the decolorization of these dyes
520 citations
TL;DR: Comparison with existing epifluorescence techniques for counting heterotrophic and phototrophic nanoplankton shows that primulin provides more accurate counts of these populations than the fluorescein isothiocyanate or proflavine techniques.
Abstract: A new method is described that uses the fluorochrome primulin and epifluorescence microscopy for the enumeration of heterotrophic and phototrophic nanoplankton (2 to 20 μm). Phototrophic microorganisms are distinguished from heterotrophs by the red autofluorescence of chlorophyll a. Separate filter sets are used which allow visualization of the primulin-stained nanoplankton without masking chlorophyll a fluorescence, thus allowing easy recognition of phototrophic cells. Comparison with existing epifluorescence techniques for counting heterotrophic and phototrophic nanoplankton shows that primulin provides more accurate counts of these populations than the fluorescein isothiocyanate or proflavine techniques. Accuracy is comparable to that with the acridine orange technique, but this method requires only one filter preparation for the enumeration of both phototrophic and heterotrophic populations. Images
487 citations
TL;DR: Several 1- and 2-carbon halogenated aliphatic organic compounds present at low concentrations were degraded under methanogenic conditions in batch bacterial cultures and in a continuous-flow meethanogenic fixed-film laboratory-scale column, suggesting that transformations of halogenation compounds can occur under meetinghanogenic Conditions in the environment.
Abstract: Several 1- and 2-carbon halogenated aliphatic organic compounds present at low concentrations (less than 100 micrograms/liter) were degraded under methanogenic conditions in batch bacterial cultures and in a continuous-flow methanogenic fixed-film laboratory-scale column. Greater than 90% degradation was observed within a 2-day detention time under continuous-flow methanogenic conditions with acetate as a primary substrate. Carbon-14 measurements indicated that chloroform, carbon tetrachloride, and 1,2-dichloroethane were almost completely oxidized to carbon dioxide, confirming removal by biooxidation. The initial step in the transformations of tetrachloroethylene and 1,1,2,2-tetrachloroethane to nonchlorinated end products appeared to be reductive dechlorination to trichloroethylene and 1,1,2-trichloroethane, respectively. Transformations of the brominated aliphatic compounds appear to be the result of both biological and chemical processes. The data suggest that transformations of halogenated aliphatic compounds can occur under methanogenic conditions in the environment.
461 citations
TL;DR: Ion-exclusion high-pressure liquid chromatography was used to measure poly-β-hydroxybutyrate in Rhizobium japonicum bacteroids andCrotonic acid formed from PHB during acid digestion was detected by its intense absorbance at 210 nm.
Abstract: Ion-exclusion high-pressure liquid chromatography (HPLC) was used to measure poly-β-hydroxybutyrate (PHB) in Rhizobium japonicum bacteroids. The products in the acid digest of PHB-containing material were fractionated by HPLC on Aminex HPX-87H ion-exclusion resin for organic acid analysis. Crotonic acid formed from PHB during acid digestion was detected by its intense absorbance at 210 nm. The Aminex-HPLC method provides a rapid and simple chromatographic technique for routine analysis of organic acids. Results of PHB analysis by Aminex-HPLC were confirmed by gas chromatography and spectrophotometric analysis.
287 citations
TL;DR: Diffusion calculations showed that formation of mats on solid substrates or of veils in the water represented optimal strategies for the bacteria to achieve a stable microenvironment, a high substrate supply, and an efficient competition with chemical sulfide oxidation.
Abstract: The interactions between colorless sulfur bacteria and the chemical microgradients at the oxygen-sulfide interface were studied in Beggiatoa mats from marine sediments and in Thiovulum veils developing above the sediments. The gradients of O2, H2S, and pH were measured by microelectrodes at depth increments of 50 μm. An unstirred boundary layer in the water surrounding the mats and veils prevented microturbulent or convective mixing of O2 and H2S. The two substrates reached the bacteria only by molecular diffusion through the boundary layer. The bacteria lived as microaerophiles or anaerobes even under stirred, oxic water. Oxygen and sulfide zones overlapped by 50 μm in the bacterial layers. Both compounds had concentrations in the range of 0 to 10 μmol liter−1 and residence times of 0.1 to 0.6 s in the overlapping zone. The sulfide oxidation was purely biological. Diffusion calculations showed that formation of mats on solid substrates or of veils in the water represented optimal strategies for the bacteria to achieve a stable microenvironment, a high substrate supply, and an efficient competition with chemical sulfide oxidation. The continuous gliding movement of Beggiatoa cells in mats or the flickering motion of Thiovulum cells in veils were important for the availability of both O2 and H2S for the individual bacteria.
TL;DR: Corn and sorghum plants grown to maturity on limiting nutrients in the greenhouse showed improved growth from inoculation approaching that of plants grown on normal nutrient concentrations.
Abstract: Inoculation of corn (Zea mays) seeds with Azospirillum brasilense strain Cd or Sp 7 significantly enhanced (30 to 50% over controls) the uptake of NO3−, K+, and H2PO4− into 3- to 4-day- and 2-week-old root segments. No gross changes in root morphology were observed; altered cell arrangement in the outer four or five layers of the cortex was seen in photomicrographs of cross sections of inoculated corn roots. The surface activity involved in ion uptake probably increased, as shown by the darker staining by methylene blue of the affected area. Shoot dry weight increased 20 to 30% in inoculated plants after 3 weeks, presumably by enhancement of mineral uptake. Corn and sorghum plants grown to maturity on limiting nutrients in the greenhouse showed improved growth from inoculation approaching that of plants grown on normal nutrient concentrations. Enhanced ion uptake may be a significant factor in the crop yield enhancement reported for Azospirillum inoculation.
TL;DR: This article corrects the article on p. 811 in vol.
Abstract: We studied the attachment of a number of freshwater bacteria from River Sowe, Coventry, England, to test substrata. The attachment of each organism to hydrophobic and hydrophilic surfaces was evaluated, and further studies evaluated the attachment of selected isolates to a number of substrata with a range of water wettabilities. The wettability of each substratum was determined by contact angle measurements and was expressed as the work of adhesion (W(A)). No generic pattern of attachment to the test surfaces was found, although the majority of the organisms isolated showed a preference for the hydrophobic surface. A more detailed study of selected isolates showed a relationship between W(A) and number of attached cells. Each bacterium attached in maximum numbers to a surface that was characteristic of that organism and that had a W(A) between 75 and 105 mJ m.
TL;DR: The results indicate that campylobacters are a normal component of the intestinal flora in several bird species, whereas Salmonella and Yersinia carriers are more sporadic.
Abstract: Cloacal swabs from 540 wild-living birds were cultured for Campylobacter fetus subsp. jejuni, Yersinia spp., and Salmonella spp. The carrier rates detected were as follows: C. fetus subsp. jejuni, 28.4%; Yersinia spp., 1.2%; and Salmonella spp., 0.8%. All birds were apparently healthy when captured. C. fetus subsp. jejuni was isolated from 11 of the 40 bird species examined. Among birds inhabiting the city of Oslo, the highest isolation rate was found in crows (Corvus corone cornix) (89.8%), followed by gulls (Larus spp.) (50.0%) and domestic pigeons (Columba livia domesticus) (4.2%). The gulls and crows scavenge on refuse dumps. High carrier rates were also detected among the following birds from nonurban, coastal areas: puffin (Fratercula arctica) (51.3%), common tern (Sterna hirundo) (5.6%), common gull (Larus canus) (18.9%), black-headed gull (Larus ridibundus) (13.2%), and herring gull (Larus argentatus) (4.2%). The list of species harboring C. fetus subsp. jejuni also includes the Ural owl (Strix uralensis), goldeneye (Bucephala clangula), and reed bunting (Emberiza schoeniclus). The following five Yersinia strains were isolated: Y. kristensenii (two strains), Y. intermedia (two strains), and "Yersinia X2" (one strain). Four strains belonging to the genus Salmonella were isolated from three different species of gulls. These isolates were identified as S. typhimurium, S. indiana, and S. djugu. The results indicate that campylobacters are a normal component of the intestinal flora in several bird species, whereas Salmonella and Yersinia carriers are more sporadic.
TL;DR: Of the 12 monosubstituted phenols studied, only p-chlorophenol and o-cresol were not significantly degraded during an 8-week incubation period, which indicated that dechlorination was the initial degradation step.
Abstract: We examined the anaerobic degradation of phenol and the ortho, meta, and para isomers of chlorophenol, methoxyphenol, methylphenol (cresol), and nitrophenol in anaerobic sewage sludge diluted to 10% in a mineral salts medium. Of the 12 monosubstituted phenols studied, only p-chlorophenol and o-cresol were not significantly degraded during an 8-week incubation period. The phenol compounds degraded and the time required for complete substrate disappearance (in weeks) were: phenol (2), o-chlorophenol (3), m-chlorophenol (7), o-methoxyphenol (2), m- and p-methoxyphenol (1), m-cresol (7), p-cresol (3), and o-, m-, and p-nitrophenol (1). Complete mineralization of phenol, o-chlorophenol, m-cresol, p-cresol, o-nitrophenol, p-nitrophenol, and o-, m-, and p-methoxyphenol was observed. In general, the presence of Cl and NO2 groups on phenols inhibited methane production. Elimination or transformation of these substituents was accompanied by increased methane production, o-Chlorophenol was metabolized to phenol, which indicated that dechlorination was the initial degradation step. The methoxyphenols were transformed to the corresponding dihydroxybenzene compounds, which were subsequently mineralized.
TL;DR: The data suggest that transformations of certain halogenated aliphatic compounds are likely to occur under denitrification conditions in the environment.
Abstract: Trihalomethanes, carbon tetrachloride, 1,1,1-trichloroethane, 1,2-dibromoethane, chlorinated benzenes, ethylbenzene, and naphthalene at concentrations commonly found in surface and groundwater were incubated under anoxic conditions to study their transformability in the presence of denitrifying bacteria. None of the aromatic compounds showed significant utilization relative to sterile controls at initial concentrations from 41 to 114 micrograms/liter after 11 weeks of incubation. Of the halogenated aliphatic compounds studied, transformations of carbon tetrachloride and brominated trihalomethanes were observed after 8 weeks in batch denitrification cultures. Carbon from the decomposition of carbon tetrachloride was both assimilated into cell material and mineralized to carbon dioxide. How this was possible remains unexplained, since carbon tetrachloride is transformed to CO2 by hydrolysis and not by oxidation-reduction. Chloroform was detected in bacterial cultures with carbon tetrachloride initially present, indicating that reductive dechlorination had occurred in addition to hydrolysis. The data suggest that transformations of certain halogenated aliphatic compounds are likely to occur under denitrification conditions in the environment.
TL;DR: The concentration of PHA relative to the bacterial biomass can reflect the recent metabolic status of the microbiota, and Gardening of sedimentary microbes by Clymenella sp.
Abstract: The procaryotic endogenous storage polymer known as poly-beta-hydroxybutyrate is actually a mixed polymer of short-chain beta-hydroxy fatty acids. A method for the quantitative recovery of this mixed polymer, called poly-beta-hydroxyalkanoate (PHA), with analysis by capillary gas-liquid chromatography, showed the presence of at least 11 short-chain beta-hydroxy acids in polymers extracted from marine sediments. Polymers extracted from Bacillus megaterium monocultures were also a complex mixture of beta-hydroxy acids with chain lengths between four and eight carbons. Lyophilized sediments were extracted in a modified Soxhlet extractor, and the polymer was purified with ethanol and diethyl ether washes. The purified polymer was treated with ethanol-chloroform-hydrochloric acid (8.5:2.5:1) for 4 h at 100 degrees C, a treatment which resulted in the formation of the ethyl esters of the constituent beta-hydroxy acids. Subsequent assay of the products by gas-liquid chromatography indicated excellent reproducibility and sensitivity (detection limit, 100 fmol). Disturbing sediments mechanically or adding natural chelators increased all major PHA components relative to the bacterial biomass. Gardening of sedimentary microbes by Clymenella sp., an annelid worm, induced decreases in PHA, with changes in the relative proportion of component beta-hydroxy acids. The concentration of PHA relative to the bacterial biomass can reflect the recent metabolic status of the microbiota.
TL;DR: Most of the lactic streptococci and a few members of the genera Clostridium, Leuconostoc, and Pediococcus were inhibited and none of the bacteriocins acted on gram-negative bacteria.
Abstract: A survey was made on the bacteriocin-producing potential of lactic streptococci. Bacteriocin-like activities were isolated and partially purified from about 5% of the 280 strains investigated. The frequency of production varied from about 1% in Streptococcus lactis subsp. diacetylactis to 9 and 7.5% in S. lactis and Streptococcus cremoris, respectively. Eight strains of S. cremoris produced bacteriocins which, on the basis of heat stability at different pH values and inhibitory spectrum, could be divided into four types. From 54 S. lactis strains, 5 strains produced inhibitory substances, namely, three nisin-like antibiotics and two different bacteriocins. Only 1 of 93 S. lactis subsp. diacetylactis strains produced a bacteriocin which was very similar to bacteriocins of type I in S. cremoris. All of the bacteriocins that were partially purified by ammonium sulfate precipitation showed very limited inhibitory spectra. Most of the lactic streptococci and a few members of the genera Clostridium, Leuconostoc, and Pediococcus were inhibited. None of the bacteriocins acted on gram-negative bacteria. The bacteriocinogenic strains were also characterized on the basis of plasmid content. All strains possessed between one and nine plasmids ranging from 1 to 50 megadaltons. Images
TL;DR: Strains of available terverticillate penicillium species and varieties were analyzed for profiles of known mycotoxins and other secondary metabolites produced on Czapek yeast autolysate agar and yeast extract-sucrose agar by using simple thin-layer chromatography screening techniques.
Abstract: Strains of available terverticillate penicillium species and varieties were analyzed for profiles of known mycotoxins and other secondary metabolites produced on Czapek yeast autolysate agar (intracellular metabolites) and yeast extract-sucrose agar (extracellular metabolites) by using simple thin-layer chromatography screening techniques These strains (2,473 in all) could be classified into 29 groups based on profiles of secondary metabolites Most of these profiles of secondary metabolites were distinct, containing several biosynthetically different mycotoxins and unknown metabolites characterized by distinct colors and retardation factors on thin-layer chromatography plates Some species (P italicum and P atramentosum) only produced one or two metabolites by the simple screening methods The 29 groups based on profiles of secondary metabolites were known species or subgroups thereof These species and subgroups were independently identifiable by using morphological and physiological criteria The species accepted, the number of isolates in each species investigated, and the mycotoxins they produced were: P atramentosum, 4; P aurantiogriseum, 510 (group I: penicillic acid and S-toxin and group II: penicillic acid, penitrem A [low frequency], terrestric acid [low frequency], viomellein, and xanthomegnin); P brevicompactum, 81 (brevianamid A and mycophenolic acid); P camembertii group I, 38, and group II, 114 (cyclopiazonic acid); P chrysogenum, 87 (penicillin, roquefortine C, and PR-toxin); P claviforme, 4 (patulin and roquefortine C); P clavigerum, 4 (penitrem A); P concentricum group I, 10 (griseofulvin and roquefortine C), and group II, 3 (patulin and roquefortine C); P crustosum, 123 (penitrem A, roquefortine C, and terrestric acid); P echinulatum, 13; P expansum, 91 (citrinin, patulin, and roquefortine C); P granulatum, 6 (patulin, penitrem A, and roquefortine C [traces]); P griseofulvum, 21 (cyclopiazonic acid, griseofulvin, patulin, and roquefortine C); P hirsutum, 100 (group I: terrestric acid; group II: citrinin, penicillic acid , roquefortine C, and terrestric acid; and group III: roquefortine C and terrestric acid), P hirsutum group IV, 2 (chaetoglobosin C); P isariiforme, 1; P italicum, 41; P mali, 104; P roquefortii, 78 (group I: mycophenolic acid, PR-toxin, and roquefortine C and group II: mycophenolic acid, patulin, penicillic acid [low frequency], and roquefortine C); P viridicatum group I, 634 (brevianamid A [low frequency], penicillic acid, viomellein, and xanthomegnin), P viridicatum group II and III, 494 (citrinin and ochratoxin A), P viridicatum group IV, 12 (griseofulvin and viridicatumtoxin) It is proposed that profiles of secondary metabolites be strongly emphasized in any future revision of the penicillia
TL;DR: Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure.
Abstract: Adaptation of microbial communities to faster degradation of xenobiotic compounds after exposure to the compound was studied in ecocores. Radiolabeled test compounds were added to cores that contained natural water and sediment. Adaptation was detected by comparing mineralization rates or disappearance of a parent compound in preexposed and unexposed cores. Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure. Adaptation was maximal after 2 weeks and was not detectable after 6 weeks. A threshold concentration of 10 ppb (10 ng/ml) was observed; below this concentration no adaptation was detected. With concentrations of 20 to 100 ppb (20 to 100 ng/ml), the biodegradation rates in preexposed cores were much higher than the rates in control cores and were proportional to the concentration of the test compound. In addition, trifluralin, 2,4-dichlorophenoxyacetic acid, and p-cresol were tested to determine whether preexposure affected subsequent biodegradation. Microbial communities did not adapt to trifluralin. Adaptation to 2,4-dichlorophenoxyacetic acid was similar to adaptation to nitrophenol. p-Cresol was mineralized rapidly in both preexposed and unexposed communities.
TL;DR: Pseudomonas aeruginosa may not be the best species for studying the later steps of the denitrification pathway because it has been well studied physiologically and genetically.
Abstract: A comparison was made of denitrification by Pseudomonas stutzeri, Pseudomonas aeruginosa, and Paracoccus denitrificans. Although all three organisms reduced nitrate to dinitrogen gas, they did so at different rates and accumulated different kinds and amounts of intermediates. Their rates of anaerobic growth on nitrate varied about 1.5-fold; concomitant gas production varied more than 8-fold. Cell yields from nitrate varied threefold. Rates of gas production by resting cells incubated with nitrate, nitrite, or nitrous oxide varied 2-, 6-, and 15-fold, respectively, among the three species. The composition of the gas produced also varied markedly: Pseudomonas stutzeri produced only dinitrogen; Pseudomonas aeruginosa and Paracoccus denitrificans produced nitrous oxide as well; and under certain conditions Pseudomonas aeruginosa produced even more nitrous oxide than dinitrogen. Pseudomonas stutzeri and Paracoccus denitrificans rapidly reduced nitrate, nitrite, and nitrous oxide and were able to grow anaerobically when any of these nitrogen oxides were present in the medium. Pseudomonas aeruginosa reduced these oxides slowly and was unable to grow anaerobically at the expense of nitrous oxide. Furthermore, nitric and nitrous oxide reduction by Pseudomonas aeruginosa were exceptionally sensitive to inhibition by nitrite. Thus, although it has been well studied physiologically and genetically, Pseudomonas aeruginosa may not be the best species for studying the later steps of the denitrification pathway.
TL;DR: V. vulnificus is a ubiquitous organism, both geographically and in a variety of environmental sources, although it occurs in relatively low numbers, and the public health significance of this organism and of the other unidentified lactose-fermenting Vibrio species is discussed.
Abstract: During the summer of 1981, 3,887 sucrose-negative vibrios were isolated from seawater, sediment, plankton, and animal samples taken from 80 sites from Miami, Fla., to Portland, Maine. Of these, 4.2% were able to ferment lactose. The lactose-positive strains isolated from the various samples correlated positively with pH and turbidity of the water, vibrios in the sediment and oysters, and total bacterial counts in oysters. Negative correlations were obtained for water salinity. Numerical taxonomy was performed on 95 of the lactose-fermenting environmental isolates and 23 reference strains. Five clusters resulted, with the major cluster containing 33 of the environmental isolates and all of the Vibrio vulnificus reference strains. The 33 isolates, which produced an acid reaction in lactose broth within hours of initial inoculation, represented 20% of all lactose-fermenting vibrios studied. These isolates were nearly identical phenotypically to clinical strains of V. vulnificus studied by the Centers for Disease Control, Atlanta, Ga., and by our laboratory, and their identification was confirmed by DNA-DNA hybridization studies. V. vulnificus was isolated from all sample types and from Miami to Cape Cod, Mass., and comparison of the environmental parameters of the eight subsites yielding this species with those of all 80 subsites revealed no significant differences. The majority of the isolates were obtained from animals, with clams providing most (84%) of these. On injection into mice, 82% of the V. vulnificus isolates resulted in death. Members of the remaining four clusters contained strains which differed from V. vulnificus in such phenotypic traits as luminescence and in urease or H2S production. None of the other reference cultures, including nine other Vibrio species, were contained in the remaining clusters, and these isolates could not be identified. Most of these were also lethal for mice. Phenotypic differences, potential pathogenicity, and geographic distribution of the five clusters were examined. It is concluded that V. vulnificus is a ubiquitous organism, both geographically and in a variety of environmental sources, although it occurs in relatively low numbers. The public health significance of this organism and of the other unidentified lactose-fermenting Vibrio species is discussed.
TL;DR: The lignin origin of APPLs was confirmed by chemical analyses, which included acidolysis, permanganate oxidation, elemental analyses, functional group analyses, nuclear magnetic resonance spectroscopy, and C isotopic techniques.
Abstract: A new, quantitatively significant intermediate formed during lignin degradation by Streptomyces viridosporus T7A was isolated and characterized. In Streptomyces-inoculated cultures, the intermediate, an acid-precipitable, polyphenolic, polymeric lignin (APPL), accumulated in the growth medium. The APPL was a water-soluble polymer probably consisting of a heterogeneous mixture of molecular weight components of ≥20,000. APPLs were precipitable from culture filtrates after they had been acidified to pH
TL;DR: The protozoan growth rates, rates of ingestion of bacteria, and final population yields generally increased with increasing bacterial concentrations, although the exact relationship varied depending on the species of bacteria used as food.
Abstract: We studied aspects of the population growth of a microflagellate, Monas sp., isolated from Lake Kinneret, Israel. The protozoan growth rates, rates of ingestion of bacteria, and final population yields generally increased with increasing bacterial concentrations, although the exact relationship varied depending on the species of bacteria used as food. Grazing rates decreased hyperbolically with increasing food density. Gross growth efficiencies and ammonia excretion rates were similar over a range of food densities among the four species of bacteria. Population doubling times and ammonia excretion rates were lowest, and growth efficiencies were highest, at temperatures between 18 and 24°C. Under optimum conditions, the microflagellates had average population doubling times of 5.0 to 7.8 h, average growth efficiencies of 23.7 to 48.7%, and average ammonia excretion rates of 0.76 to 1.23 μmol of NH4+ per mg (dry wt) per h.
TL;DR: Characterization of the wild-type and SA-1 strain in 6% ECB demonstrated the superiority of the latter in terms of growth rate, time of onset of butanol production, carbohydrate utilization, pH resistance, and final butanol concentration in the fermentation broth.
Abstract: By employing serial enrichment, a derivative of Clostridium acetobutylicum ATCC 824 was obtained which grew at concentrations of butanol that prevented growth of the wild-type strain. The parent strain demonstrated a negative growth rate at 15 g of butanol/liter, whereas the SA-1 mutant was still able to grow at a rate which was 66% of the uninhibited control. SA-1 produced consistently higher concentrations of butanol (from 5 to 14%) and lower concentrations of acetone (12.5 to 40%) than the wild-type strain in 4 to 20% extruded corn broth (ECB). Although the highest concentration of butanol was produced by SA-1 and the wild-type strain in 14% ECB, the best solvent ratio with respect to optimizing butanol and decreasing acetone occurred between 4 and 8% ECB for SA-1. SA-1 demonstrated higher conversion efficiency to butanol than the wild-type strain at every concentration of ECB tested. Characterization of the wild-type and SA-1 strain in 6% ECB demonstrated the superiority of the latter in terms of growth rate, time of onset of butanol production, carbohydrate utilization, pH resistance, and final butanol concentration in the fermentation broth.
TL;DR: The substrate and growth conditions used by Penicillium taxonomists proved suitable for the production of the mycotoxins investigated when 60 known toxigenic isolates and 865 cultures isolated from foods and feedstuffs were tested with this screening method.
Abstract: A simple screening method for molds producing the intracellular mycotoxins brevianamide A, citreoviridin, cyclopiazonic acid, luteoskyrin, penitrem A, roquefortine C, sterigmatocystin, verruculogen, viomellein, and xanthomegnin was developed. After removing an agar plug from the mold culture, the mycelium on the plug is wetted with a drop of methanol-chloroform (1:2). By this treatment the intracellular mycotoxins are extracted within seconds and transferred directly to a thin-layer chromatography plate by immediately placing the plug on the plate while the mycelium is still wet. After removal of the plug, known thin-layer chromatographic procedures are carried out. The substrate (Czapek yeast autolysate agar) and growth conditions (25 degrees C for 7 days) used by Penicillium taxonomists proved suitable for the production of the mycotoxins investigated when 60 known toxigenic isolates and 865 cultures isolated from foods and feedstuffs were tested with this screening method.
TL;DR: A novel oxygen microelectrode with a tip diameter of 2 to 20 mum was constructed which could function satisfactorily under a variety of environmental conditions and in a range of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil.
Abstract: A novel oxygen microelectrode with a tip diameter of 2 to 20 μm was constructed which could function satisfactorily under a variety of environmental conditions and in a variety of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil. Measurement of oxygen by this electrode does not require stirring of the medium. Electrodes could be made so that the 90% response time necessary to detect changes in oxygen concentration was less than 0.2 s, and response was linear with oxygen concentration. To demonstrate the performance of the electrode, oxygen and photosynthesis profiles of an acid microbial mat (pH 2.8) dominated by the eucaryotic alga Cyanidium caldarium were made. Photosynthetic rates as high as 95 mmol of O2 dm−3 h−1 were measured within the most active 0.1-mm layer, which was ca. 0.2 mm below the surface of the microbial mat. The total photosynthetic activity was 47 mmol of O2 m−2 h−1. Vertical profiles of photosynthesis at different light intensities showed that the microalgae within the mat were not photoinhibited at bright sunlight (2,090 μEinsteins m−2 s−1).
TL;DR: The specific volume of wet cells as measured in density gradients of colloidal silica was correlated with the percent dry weight of the cells and found to be in general agreement with calculations based on the partial specificVolume of major cell components.
Abstract: Several isolates of bacteria and fungi from soil, together with cells released directly from soil, were studied with respect to buoyant density and dry weight. The specific volume (cubic centimeters per gram) of wet cells as measured in density gradients of colloidal silica was correlated with the percent dry weight of the cells and found to be in general agreement with calculations based on the partial specific volume of major cell components. The buoyant density of pure bacterial cultures ranged from 1.035 to 1.093 g/cm3, and their dry-matter content ranged from 12 to 33% (wt/wt). Average values proposed for the conversion of bacterial biovolume into biomass dry weight are 1.09 g/cm3 and 30% dry matter. Fungal hyphae had buoyant densities ranging from 1.08 to 1.11 g/cm3, and their dry-matter content ranged from 18 to 25% (wt/wt). Average values proposed for the conversion of hyphal biovolume into biomass dry weight are 1.09 g/cm3 and 21% dry matter. Three of the bacterial isolates were found to have cell capsules. The calculated buoyant density and percent dry weight of these capsules varied from 1.029 g/cm3 and 7% dry weight to 1.084 g/cm3 and 44% dry weight. The majority of the fungi were found to produce large amounts of extracellular material when grown in liquid cultures. This material was not produced when the fungi were grown on either sterile spruce needles or membrane filters on an agar surface. Fungal hyphae in litter were shown to be free from extracellular materials.
TL;DR: It is suggested that acetate is a major electron donor for sulfate reduction in marine sediments, and in the presence of high concentrations of sulfate, methane may be derived from novel substrates such as methylamine.
Abstract: The activity of and potential substrates for methane-producing bacteria and sulfate-reducing bacteria were examined in marsh, estuary, and beach intertidal sediments. Slow rates of methane production were detected in all sediments, although rates of sulfate reduction were 100- to 1,000-fold higher. After sulfate was depleted in sediments, the rates of methane production sharply increased. The addition of methylamine stimulated methanogenesis in the presence of sulfate, and [C]methylamine was rapidly converted to CH(4) and CO(2) in freshly collected marsh sediment. Acetate, hydrogen, or methionine additions did not stimulate methanogenesis. [methyl-C]methionine and [2-C]acetate were converted to CO(2) and not to CH(4) in fresh sediment. No reduction of CO(2) to CH(4) occurred in fresh sediment. Molybdate, an inhibitor of sulfate reduction, inhibited [2-C]acetate metabolism by 98.5%. Fluoracetate, an inhibitor of acetate metabolism, inhibited sulfate reduction by 61%. These results suggest that acetate is a major electron donor for sulfate reduction in marine sediments. In the presence of high concentrations of sulfate, methane may be derived from novel substrates such as methylamine.
TL;DR: Results from experiments with molybdate and 2-bromoethanesulfonic acid suggested that methanol was oxidized primarily through sulfate reduction, and trimethylamine accounted for 35.1 to 61.1% of total methane production.
Abstract: The fates and the rates of metabolism of acetate, trimethylamine, methylamine, and methanol were examined to determine the significance of these compounds as in situ methane precursors in surface sediments of an intertidal zone in Maine. Concentrations of these potential methane precursors were generally 8 h) and were characterized by formation of both 14CH4 and 14CO2. Ratios of 14CH4/14CO2 from [14C]trimethylamine and methylamine in uninhibited sediments indicated that a significant fraction of these substrates were catabolized via a non-methanogenic process. Data from inhibition experiments involving sodium molybdate and 2-bromoethanesulfonic acid supported this interpretation. [14C]methanol was oxidized relatively slowly compared with the other substrates and was catabolized mainly to 14CO2. Results from experiments with molybdate and 2-bromoethanesulfonic acid suggested that methanol was oxidized primarily through sulfate reduction. In Lowes Cove sediments, trimethylamine accounted for 35.1 to 61.1% of total methane production.