Showing papers on "Bacteria published in 1982"

Treatment of Gram-Negative Bacteremia and Shock with Human Antiserum to a Mutant Escherichia coli

Abstract: In an effort to decrease deaths from gram-negative bacteremia and endotoxin shock, we treated bacteremic patients with human antiserum to endotoxin (lipopolysaccharide) core. Antiserum was prepared by vaccinating healthy men with heat-killed Escherichia coli J5; this mutant lacks lipopolysaccharide oligosaccharide side chains, so that the core, which is nearly identical to that of most other gram-negative bacteria, is exposed for antibody formation. In a randomized controlled trial, patients were given either J5 antiserum or preimmune control serum intravenously, near the onset of illness. The number of deaths in the bacteremic patients was 42 of 109 (39 per cent) in controls and 23 of 103 (22 per cent) in recipients of J5 antiserum (P = 0.011). In those with profound shock, mortality was 30 of 39 (77 per cent) in controls and 18 of 41 (44 per cent) in recipients of J5 antiserum (P = 0.003). We conclude that human antiserum to the lipopolysaccharide core can substantially reduce deaths from gram-negative bacteremia.

Nonstaining (KOH) method for determination of gram reactions of marine bacteria.

Abstract: A rapid nonstaining (KOH) method for the determination of the Gram reactions of bacteria is described, and its application to marine isolates is discussed. All gram-positive and gram-negative results obtained by Gram staining were confirmed by the KOH method. Gram-variable bacteria produced equivocal results.

Chlorine Resistance Patterns ofBacteria fromTwoDrinking WaterDistribution Systems

Abstract: microorganisms inchlorinated waters. Bacteriaretained onthesurfaces of2.0-p.m Nuclepore membranefilters weresignificantly moreresistant tofree chlorine compared tothetotal microbial population recovered on0.2-p.m membrane filters, presumably because aggregated cells or bacteria attached tosuspended particulate matterexhibit moreresistance than unassociated microorganisms. Inaccordance withthishypothesis, scanning electron microscopy ofsuspended particulate matterfromthewatersamples revealed thepresence ofattached bacteria. Themostresistant microorganisms wereabletosurvive a2-min exposure to10mgoffree chlorine perliter. These included gram-positive spore-forming bacilli, actinomycetes, andsomemicrococci.Themostsensitive bacteria werereadily killed bychlorine concentrations of 1.0mgliter-' orless, andincluded mostgram-positive micrococci, CorynebacteriumlArthrobacter, Klebsiella, PseudomonaslAlcaligenes, FlavobacteriumIMoraxella, andAcinetobacter.

Influence of plant phenolic acids on growth and cellulolytic activity of rumen bacteria.

Abstract: Isolated rumen bacteria were examined for growth and, where appropriate, for their ability to degrade cellulose in the presence of the hydroxycinnamic acids trans-p-coumaric acid and trans-ferulic acid and the hydroxybenzoic acids vanillic acid and 4-hydroxybenzoic acid. Ferulic and p-coumaric acids proved to be the most toxic of the acids examined and suppressed the growth of the cellulolytic strains Ruminococcus albus, Ruminococcus flavefaciens, and Bacteroides succinogenes when included in a simple sugars medium at concentrations of >5 mM. The extent of cellulose digestion by R. flavefaciens and B. succinogenes but not R. albus was also substantially reduced. Examination of rumen fluid from sheep maintained on dried grass containing 0.51% phenolic acids showed the presence of phloretic acid (0.1 mM) and 3-methoxyphloretic acid (trace) produced by hydrogenation of the 2-propenoic side chain of p-coumaric and ferulic acids, respectively. The parent acids were found in trace amounts only, although they represented the major phenolic acids ingested. Phloretic and 3-methoxyphloretic acids proved to be considerably less toxic than their parent acids. All of the cellulolytic strains (and Streptococcus bovis) showed at least a limited ability to hydrogenate hydroxycinnamic acids, with Ruminococcus spp. proving the most effective. No further modification of hydroxycinnamic acids was produced by the single strains of bacteria examined. However, a considerable shortfall in the recovery of added phenolic acids was noted in media inoculated with rumen fluid. It is suggested that hydrogenation may serve to protect cellulolytic strains from hydroxycinnamic acids.

Chlorine resistance patterns of bacteria from two drinking water distribution systems.

Abstract: The relative chlorine sensitivities of bacteria isolated from chlorinated and unchlorinated drinking water distribution systems were compared by two independent methods. One method measured the toxic effect of free chlorine on bacteria, whereas the other measured the effect of combined chlorine. Bacteria from the chlorinated system were more resistant to both the combined and free forms of chlorine than those from the unchlorinated system, suggesting that there may be selection for more chlorine-tolerant microorganisms in chlorinated waters. Bacteria retained on the surfaces of 2.0-microns Nuclepore membrane filters were significantly more resistant to free chlorine compared to the total microbial population recovered on 0.2-micron membrane filters, presumably because aggregated cells or bacteria attached to suspended particulate matter exhibit more resistance than unassociated microorganisms. In accordance with this hypothesis, scanning electron microscopy of suspended particulate matter from the water samples revealed the presence of attached bacteria. The most resistant microorganisms were able to survive a 2-min exposure to 10 mg of free chlorine per liter. These included gram-positive spore-forming bacilli, actinomycetes, and some micrococci. The most sensitive bacteria were readily killed by chlorine concentrations of 1.0 mg liter-1 or less, and included most gram-positive micrococci, Corynebacterium/Arthrobacter, Klebsiella, Pseudomonas/Alcaligenes, Flavobacterium/Moraxella, and Acinetobacter.

Antimicrobial properties of diacetyl.

Abstract: Diacetyl preparations from three commercial sources were found to be essentially similar when tested primarily against a set of 40 cultures, including 10 of lactic acid bacteria, 4 of yeasts, 12 of gram-positive non-lactic acid bacteria, and 14 of gram-negative bacteria. The compound was effective at pH less than or equal to 7.0 and progressively ineffective at pH greater than 7.0. The lactic acid bacteria were essentially unaffected by concentrations between 100 and 350 micrograms/ml over the pH range of 5.0 to 7.0. Of the 12 gram-positive non-lactic acid bacteria, 11 were inhibited by 300 micrograms/ml at pH less than or equal to 7.0. The three yeasts and the 13 gram-negative bacteria that grew at pH 5.5 were inhibited by 200 micrograms/ml. Diacetyl was ineffective against four clostridia under anaerobic conditions. It was lethal for gram-negative bacteria and generally inhibitory for gram-positive bacteria. Nongrowing cells were not affected. The effectiveness of diacetyl was considerably less in brain heart infusion broth, Trypticase soy agar, and cooked-meat medium than in nutrient broth or plate count agar. The antimicrobial activity was antagonized by glucose, acetate, and Tween 80 but not by gluconic acid. As an antimicrobial agent, diacetyl was clearly more effective against gram-negative bacteria, yeasts, and molds than against gram-positive bacteria.

Erythrobacter longus gen. nov., sp. nov., an Aerobic Bacterium Which Contains Bacteriochlorophyll a

Abstract: Four orange-pigmented and seven pink-pigmented strains of bacteria which contained bacteriochlorophyll a were isolated from high-tidal seaweeds, such as Enteromorpha linza (L.) J. Ag. and Porphyra sp. All of the isolates were gram negative. The orange-pigmented bacteria were rods with parallel sides and rounded ends, and the pink-pigmented bacteria were ovoids and short rods. All were motile by means of subpolar flagella. None of the strains produced growth anaerobically in the light. No growth occurred with an atmosphere containing H2 and CO2. All of these bacteria grew aerobically and utilized glucose, pyruvate, acetate, butyrate, and glutamate as sole organic carbon sources. The best growth occurred on complex media formulated for heterotrophic marine bacteria. Biotin was required. Oxidase and catalase were present. Small amounts of acid were produced from a wide range of carbohydrates under microaerobic conditions. Gelatin was hydrolyzed. The strains which we investigated fell into the following three clusters: cluster A, all of the orange strains; cluster B, three pink strains; and cluster C, four pink strains. The strains of clusters B and C required thiamine and nicotinic acid and were susceptible to streptomycin. Tween 80 was hydrolyzed and phosphatase activity was produced by the strains of clusters A and B. Pantothenate was required only by the strains of cluster C. The guanine-plus-cytosine contents of the deoxyribonucleic acids of these organisms ranged from 60 to 64 mol%. These organisms are recognized here as members of a new genus, Erythrobacter. Although these organisms did not grow phototrophically, the presence of bacteriochlorophyll a indicated that they are most closely related to the Rhodospirillaceae. The type species is Erythrobacter longus, the type strain of which is an orange strain, OCh101 (= IFO 14126).

Nitrous Oxide Production by Organisms Other than Nitrifiers or Denitrifiers

Abstract: Heterotrophic bacteria, yeasts, fungi, plants, and animal breath were investigated as possible sources of N2O. Microbes found to produce N2O from NO3− but not consume it were: (i) all of the nitrate-respiring bacteria examined, including strains of Escherichia, Serratia, Klebsiella, Enterobacter, Erwinia, and Bacillus; (ii) one of the assimilatory nitrate-reducing bacteria examined, Azotobacter vinelandii, but not Azotobacter macrocytogenes or Acinetobacter sp.; and (iii) some but not all of the assimilatory nitrate-reducing yeasts and fungi, including strains of Hansenula, Rhodotorula, Aspergillus, Alternaria, and Fusarium. The NO3−-reducing obligate anaerobe Clostridium KDHS2 did not produce N2O. Production of N2O occurred only in stationary phase. The nitrate-respiring bacteria produced much more N2O than the other organisms, with yields of N2O ranging from 3 to 36% of 3.5 mM NO3−. Production of N2O was apparently not regulated by ammonium and was not restricted to aerobic or anaerobic conditions. Plants do not appear to produce N2O, although N2O was found to arise from some damaged plant tops, probably due to microbial growth. Concentrations of N2O above the ambient level in the atmosphere were found in human breath and appeared to increase after a meal of high-nitrate food.

Seasonal dynamics of elemental sulfur in two coastal sediments

Abstract: A spectrophotometric method for elemental sulfur (S0) analysis without interference from other reduced sulfur compounds was adapted for the use in reducing sediments. The S0 distribution in two coastal sediments was studied regularly from summer to winter and compared to factors regulating the S0 accumulation, such as redox potentials, the rate of bacterial sulfide production and the general sulfur chemistry. Dense coatings of sulfur bacteria developed on the sediment surface of a sulfuretum which had an S0 concentration of up to 41 μmol S cm−3. The 2·5-mm thick bacterial coating contained 40% of all S0 in the sediment. A more typical marine sediment with a few cm thick oxidized surface layer had an S0 maximum of 1–3 μmol S cm−3 at 2–4 cm depth. The S0 maximum in both sediments increased from summer to winter as the sediments gradually became more oxidized. The deeper layers maintained a low S0 concentration. Most of the S0 in the upper few mm of a laboratory sulfuretum was present inside sulfur bacteria and actively migrated up and down with the bacteria depending upon the changing light and oxygen conditions.

Effect of pyochelin on the virulence of Pseudomonas aeruginosa.

Abstract: A virulent isolate of Pseudomonas aeruginosa PAO1, which had been obtained from eight sequential intraperitoneal infections in mice compromised with iron and methotrexate, expressed greater lethality than the avirulent parent strain when both strains were injected into mice treated with iron. The present study demonstrates that pyochelin, a siderophore produced by P. aeruginosa, also increases the lethality of the virulent bacteria but not of the avirulent bacteria. Analysis of the growth and clearance of both virulent and avirulent strains in mice revealed that pyochelin increased the growth and lethality of virulent bacteria but only increased the survival of the avirulent bacteria. A streptomycin-dependent mutant of strain PAO1 (strd1) was used to demonstrate that pyochelin did not affect the clearance activity of mice. This strongly suggests that the effects of pyochelin in stimulating the persistence of avirulent bacteria and in increasing the lethality of virulent bacteria are due solely to the promotion of bacterial growth. Since the virulent bacteria were equivalent to the avirulent bacteria in utilizing pyochelin during in vitro growth in the presence of transferrin, it appears that the stimulation of growth by pyochelin allows the expression of additional virulence properties by the virulent bacteria.

Adherence of Shigella flexneri to guinea pig intestinal cells is mediated by a mucosal adhesion.

Abstract: Guinea pig colonic epithelial cells released by treating sections of the colon with solutions containing EDTA, dithiothreitol, and citrate avidly adhered Shigella flexneri bacteria. Separation of the intestinal cells from nonbound bacteria was achieved by differential sedimentation on a Percoll gradient. Adherence of S. flexneri to the colonic cells was Ca2+ (1 mM) and time dependent. The pH optimum was pH 6.2, and almost no attachment (less than 5%) was observed at low temperature (4 degrees C). The average number of bacteria which bound to colonic cells was 70 bacteria per cell, whereas attachment to cells isolated from the ileum region was 6 bacteria per cell. Colonic cells obtained from the intestine of rabbits or rats did not adhere Shigella. Adherence to guinea pig colonic cells was inhibited (50%) by several carbohydrates, such as 0.1% fucose or 0.5% glucose, as well as by a lipopolysaccharide preparation (10 micrograms /ml) isolated from S. flexneri. Fixation of the bacteria with glutaraldehyde or preincubation of the bacteria with lectins or proteolytic enzymes did not affect their adherence. Proteolytic digestions or fixation of the epithelial cells, as well as pretreatments with lipopolysaccharide or fucose solutions, abolished their ability to adhere bacteria. These results indicate that a carbohydrate-binding substance on the surface of guinea pig colonic epithelial cells is responsible for the attachment of the Shigella bacilli.

The normal human anaerobic microflora.

Abstract: Anaerobic bacteria are prevalent among the bacterial populations of the human body, particularly on mucous membrane surfaces The major sites with a rich anaerobic normal microflora are the mouth, the gastrointestinal tract and the female genital tract The oral cavity harbours more than 300 different bacterial species The concentrations of bacteria in saliva are 10(8) to 10(9) colony forming units/ml and anaerobic bacteria outnumber aerobic bacteria by 10:1 On the tooth surfaces, the concentrations of bacteria are 10(10) to 10(11) cfu/ml with a predominance of anaerobes Bacterial concentrations in gingival scrapings are 10(11) to 10(12) cfu/ml with anaerobic bacteria outnumbering aerobic bacteria by 1000:1 In the saliva and on the tongue surface, the predominant anaerobic bacteria are cocci, while in the gingival crevice large concentrations of gram-negative rods are recovered Microorganisms found in the upper intestinal tract are different from those in the lower intestinal tract In the stomach and the proximal small bowel, the microorganisms found as normal flora are a reflection of the oral flora Bacterial concentrations in this region are 10(2)-10(5) cfu/ml intestinal content In the colon, bacterial concentrations of 10(11)-10(12) cfu/g faeces are found About 500 different bacterial species are recovered in the lower intestine The most common anaerobic microorganisms are bifidobacteria, lactobacilli and bacteroides Recent studies have used quantitative techniques for analyses of the vaginal flora and it has been found that anaerobic bacteria outnumber aerobic bacteria in the vagina by approximately 10:1 The most prevalent bacteria are peptococci, present in counts of 10(7)-10(8) cfu/ml Lactobacilli, corynebacteria, eubacteria and bacteroides are also isolated

Selection of antibiotic-resistant standard plate count bacteria during water treatment.

Abstract: Standard plate count (SPC) bacteria were isolated from a drinking-water treatment facility and from the river supplying the facility. All isolates were identified and tested for their resistance to six antibiotics to determine if drug-resistant bacteria were selected for as a consequence of water treatment. Among the isolates surviving our test procedures, there was a significant selection (P less than 0.05) of gram-negative SPC organisms resistant to two or more of the test antibiotics. These bacteria were isolated from the flash mix tank, where chlorine, alum, and lime are added to the water. Streptomycin resistance in particular was more frequent in this population as compared with bacteria in the untreated river water (P less than 0.01). SPC bacteria from the clear well, which is a tank holding the finished drinking water at the treatment facility, were also more frequently antibiotic resistant than were the respective river water populations. When 15.8 and 18.2% of the river water bacteria were multiply antibiotic resistant, 57.1 and 43.5%, respectively, of the SPC bacteria in the clear well were multiply antibiotic resistant. Selection for bacteria exhibiting resistance to streptomycin was achieved by chlorinating river water in the laboratory. We concluded that the selective factors operating in the aquatic environment of a water treatment facility can act to increase the proportion of antibiotic-resistant members of the SPC bacterial population in treated drinking water.

Preparation of the cellulase from the cellulolytic anaerobic rumen bacterium Ruminococcus albus and its release from the bacterial cell wall

Abstract: 1. Most of the cellulase (CM-cellulase) elaborated by the rumen bacterium Ruminococcus albus strain SY3, which was isolated from a sheep, was cell-wall-bound. 2. The enzyme could be released readily by washing either with phosphate buffer or with water. 3. The amount of enzyme released was affected by the pH and ionic strength of the phosphate buffer. 4. The cell-wall-bound enzyme was of very high molecular weight (>>1.5x10(6)) as judged by its chromatographic behaviour on Sephacryl S-300. 5. The molecular weight of the extracellular enzyme was variable and depended on the culture conditions. 6. When cellobiose was used as the energy source and the medium contained rumen fluid (30%), the extracellular enzyme was, in the main, of high molecular weight. 7. When cellulose replaced the cellobiose, the cell-free culture filtrate contained only low-molecular-weight enzyme (M(r) approx. 30000) in late-stationary-phase cultures (7 days). 8. Cultures that did not contain rumen fluid contained mainly low-molecular-weight enzyme. 9. Under some conditions the high-molecular-weight enzyme could be broken down to some extent into low-molecular-weight enzyme by treatment with dissociating agents. 10. Cell-free and cell-wall-bound enzymes showed the same relationship when the change in fluidity effected by them on a solution of CM-cellulose was plotted against the corresponding increase in reducing sugars, suggesting that the enzymes were the same. 11. It is possible that R. albus cellulase exists as an aggregate of low-molecular-weight cellulase components on the bacterial cell wall and in solution under certain conditions.

Effect of organic matter on growth and cell yield of ammonia-oxidizing bacteria

Abstract: The effect of various organic compounds on the growth of ammonia-oxidizing bacteria was examined.Nitrosococcus oceanus, a strongly halophilic bacterium, had a very low tolerance to organic matter compared with other organisms tested. Organic compounds scarcely affected the growth of theNitrosomonas strains whereas nitrite formation by bothNitrosococcus mobilis strains was inhibited by nearly all of the substances tested. The growth ofNitrosospira strain Nsp1 was enhanced more than 30% by acetate and formate, but not growth was detectable in the presence of pyruvate. On the contrary,Nitrosospira strain Nsp5 was stimulated only by pyruvate. Nitrite formation by the twoNitrosovibrio tenuis strains tested was similar. The growth of both strains was enhanced considerably by formate and glucose; acetate and, to a greater extent, pyruvate inhibited these bacteria. In batch culture, the energy efficiency of autotrophically grown ammonia-oxidizing bacteria varied from strain to strain. The cell yield of mixotrophically grown cultures, per unit of ammonia oxidized, was increased in comparison with autotrophic ones. No heterotrophic growth was detected.

Cellular Location and Some Properties of Proteolytic Enzymes of Rumen Bacteria

Abstract: Several physical and chemical techniques were used to extract, and to identify the location of, proteolytic enzymes associated with mixed rumen bacteria. Most activity was removable by gentle physical methods such as shaking and brief blending, without cell disruption, indicating that it was associated with coat and capsular material. Proteases were present also in the cell envelope, corresponding to the inner membrane fraction of gram-negative bacteria, and intracellularly and were removable by detergent and French press treatment. Temperature and pH profiles were obtained for the coat enzymes, likely to be the most important in the digestion of food protein. Inhibition studies indicated that these proteases, and those of the whole bacterial fraction from rumen fluid, were predominantly of the cysteine protease type.

Attachment and ingestion of bacteria by trophozoites of Entamoeba histolytica

Abstract: Entamoeba histolytica trophozoites were found to be very selective in their interactions with bacteria. Two principal mechanisms were shown to be responsible for these interactions. Certain bacteria, such as a number of Escherichia coli and Serratia marcescens strains which are known to contain mannose-binding components on their cell surface, bound to mannose receptors on the amoeba membrane. This attachment was markedly inhibited by alpha-methylmannoside (0.5%), especially when the incubations were done at low temperature (5 degrees C). Other bacterial species, such as Shigella flexneri and Staphylococcus aureus, which do not possess a mannose-binding capacity, attached to the amoebae, but only with the aid of concanavalin A or after opsonization of the bacteria with immune serum. In both types of attachment, between 40 and 100 bacteria bound per amoeba, and considerable ingestion of bacteria into amoeba vacuoles was observed at 37 degrees C. The attachment of opsonized bacteria to the amoebae does not appear to be mediated by Fc receptors since Fab9 dimers obtained after pepsin digestion of immunoglobulin were capable of mediating adherence. Furthermore, preincubation of the amoebae with aggregated human immunoglobulin G or with heat-inactivated immune serum and EDTA did not inhibit the attachment of opsonized bacteria. The attachment of opsonized bacteria was markedly inhibited by N-acetylglucosamine-containing glycoconjugates, such as peptidoglycan and chitin oligosaccharides, as well as by N-acetylgalactosamine. These results indicate that amoebae can attach and ingest bacteria either by using their membrane-associated carbohydrate-binding protein or by having their mannose-containing cell surface components serve as receptors. Images

Degradation of bacteria by Mytilus edulis

Abstract: The uptake of several species of bacteria by the common mussel Mytilus edulis (L.) and the subsequent fate of some polymers of the bacteria have been investigated in a study carried out during 1981. Bacteria (Escherichia coli, Micrococcus luteus, M. roseus, Bacillus cereus, Staphylococcus aureus and a marine pseudomonad, 1-1-1) were radiolabelled by growth in medium containing 3H-thymidine and the uptake of bacteria by Mytilus edulis was monitored. Labelled and unlabelled bacteria, at initial concentrations of 0.5 to 1x107 bacteria ml-1, were cleared at similar, exponential rates with no significant difference in the rates for different bacteria: 90% of bacteria were cleared in a mean time of 1.93±0.12 h (SEM, n=63). Those bacteria with cell walls which were sensitive to M. edulis lysozyme were rapidly degraded by the mussel and 3H-labelled DNA was released in a form not precipitable by 10% trichloroacetic acid. Lysozyme-resistant bacteria (Micrococcus roseus and S. aureus) were cleared from suspension by Mytilus edulis but most were rejected intact. By measuring the rate of release of 3H-thymidine-labelled material from the mussel the rate of degradation of lysozyme-sensitive bacteria by M. edulis was found. For different bacteria the degradation rate varied from approx 2x108 to 27x108 bacteria h-1 with an overall mean of 10x108 bacteria h-1. A thymidine- and diaminopimelicacid-requiring auxotroph of E. coli was radiolabelled with 3H-thymidine, 3H-diaminopimelic acid or 14C-glucose and fed to M. edulis. Bacteria were cleared and degraded by the mussel; 3H-diaminopimelic acid-labelled or 14C-glucose-labelled polymers were retained, whereas 3H-thymidine-labelled polymers were released into the surrounding water. Extracts of the digestive gland of M. edulis degraded lysozyme-sensitive bacteria to release 3H-thymidine-labelled material, but did not release 3H-thymidine-labelled material from lysozyme-resistant bacteria. It is concluded that M. edulis can select lysozymesensitive bacteria for subsequent processing and discriminate between bacterial polymers to reject DNA. Also, bacteria could provide a substantial fraction of the carbon requirement of the mussel.

Interactions between amino-acid-degrading bacteria and methanogenic bacteria in anaerobic digestion

Abstract: The degradation of amino acids in anaerobic digestion was examined in terms of the interactions between amino-acid-degrading bacteria and methanogenic bacteria. Certain amino acids were degraded oxidatively by dehydrogenation, with methanogenic bacteria acting as H(2) acceptors. The inhibition of methanogenesis by chloroform also inhibited the degradation of these amino acids and/or caused variations in the composition of volatile acids produced from them. The presence of glycine reduced the inhibitory effect caused by chloroform, probably because glycine acted as an H(2) acceptor in place of methanogenic bacteria. This fact suggested that the coupled oxidation-reduction reactions between two amino acids-one acting as the H(2) donor and the other acting as the H(2) acceptor-may occur in the anaerobic digestion of proteins or amino-acid mixtures. The conversion of some proteins to volatile acids was not affected when methanogenesis was inhibited by chloroform. This suggested that the component amino acids of proteins may be degraded by the coupled oxidation-reduction reactions and that the degradation of proteins may not be dependent on the activity of methanogenic bacteria as H(2) acceptors.

Ultrastructure of bacteria and the proportion of Gram-negative bacteria in marine sediments

Abstract: Bacteria in sediments from the surface aerobic layer (0-1 cm) and a deeper anaerobic layer (20-21 cm) of a seagrass bed were examined in section by transmission electron microscopy. Bacteria with a Gram-negative ultrastructure made up 90% of bacteria in the surface layer, and Gram-positive bacteria comprised 10%. In the anaerobic zone, Gram-negative bacteria comprised 70% and Gram-positive bacteria 30% of the bacterial population. These differences were highly significant and support predictions of these proportions made from muramic acid measurements and direct counting with fluorescence microscopy. Most cells were enveloped in extracellular slime layers or envelopes, some with considerable structural complexity. The trophic value to animals of these envelopes is discussed. A unique organism with spines was observed.

Primary photochemistry in the facultatively aerobic green photosynthetic bacterium Chloroflexus aurantiacus

Abstract: Photochemical activity was examined in membrane fragments and a purified membrane preparation from Chloroflexus. Flash-induced absorption difference spectroscopy strongly suggests a primary donor (P865) that is more similar to the P870 bacteriochlorophyll a dimer found in the purple photosynthetic bacteria than it is to P840 found in the anaerobic green bacteria. Redox measurements on P865 and an early acceptor also indicate a photochemical system characteristic of the purple bacteria. The membrane preparation contains a tightly bound type c cytochrome, c554, that is closely coupled to the reaction center as indicated by its ability to rereduce photooxidized P865. Chloroflexus thus appears to be distinct photochemically from other families of photosynthetic bacteria and may occupy an important role in photosynthetic evolution.

The myxovirescins, a family of antibiotics from Myxococcus virescens (Myxobacterales).

Abstract: The myxobacterium, Myxococcus virescens strain Mx v48 produced a family of at least 12 closely related antibiotics, the myxovirescins***. At a concentration of 1 to 5 μg/ml, the main component, myxovirescin A, was bactericidal for many Gram-negative bacteria, in particular enterobacteria, and at 20 to 50 μg/ml it also inhibited some pseudomonads and Gram-positive bacteria. The antibiotics seem to interfere with cell wall synthesis. The molecular formula of myxovirescin A was C35H61NO8. It is a new antibiotic.

Production and properties of cyanobacterial endotoxins.

Abstract: Lipopolysaccharides (LPS) were isolated from four species of cyanobacteria (Anabaena flos-aquae UTEX 1444. A. cylindrica, Oscillatoria tenuis, and O. brevis) frequently occurring in drinking-water supplies. The cyanobacterial LPS contained glucose, xylose, mannose, and rhamnose, but differed from the LPS derived from most gram-negative bacteria because of the variable presence of 2-keto-3-deoxyoctonate, heptose, galactose, and glucosamine. Cyanobacterial lipid A is characterized by long-chain saturated an unsaturated fatty acids and hydroxy fatty acids which show great diversity. Unlike lipid A from heterotrophic gram-negative bacteria, lipid A from cyanobacteria usually lacks phosphates. The detection of distinct O-antigen chemotypes indicates that LPS may be used for taxonomic classification. Isolated cyanobacterial LPS always induced Limulus amoebocyte lysate gelation. A. flos-aquae LPS gave a positive Schwartzman reaction. Endotoxins from A. cylindrica and O. brevis were toxic to mice when injected intraperitoneally. The cyanobacterial endotoxins showed generally lower biological activity than did LPS derived from common heterotrophic gram-negative bacteria. Nevertheless, cyanobacteria in algal blooms may be a significant source of endotoxins in water supplies.

Energy conversion by plants and bacteria

Abstract: Energy conversion by plants and bacteria , Energy conversion by plants and bacteria , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

D-Gluconate dehydrogenase from bacteria, 2-keto-D-gluconate-yielding, membrane-bound.

Abstract: Publisher Summary This chapter describes an assay method for the isolation of D-gluconate dehydrogenase from bacteria. D-gluconate dehydrogenase occurs on the outer surface of cytoplasmic membrane of oxidative bacteria, such as Pseudomonas, Klebsiella, Serratia , and acetic acid bacteria. The enzyme activity is linked to the electron transport chain in the cytoplasmic membrane constituting a D-gluconate oxidase system. The assay is performed spectrophotometrically at 25°C by measuring the decrease of absorbance at 600 nm of 2,6-dichlorophenolindophenol (DCIP) mediated with phenazine methosulfate (PMS). The activity is also measured with PMS, DCIP, ferricyanide, or coenzyme Q (CoQ) as an electron acceptor. The purification procedures of the enzyme from P. fluorescens and K. pneumoniae are described in the chapter. Potassium phosphate buffer, pH 6.0, containing 5 m M MgCl 2 is used throughout the purification of P. fluorescens . The steps involved in the purification procedure are (1) the preparation of membrane fraction, (2) the solubilization of enzyme, (3) ammonium sulfate fractionation, and (4) hydroxyapatite column chromatography. Purified D-gluconate dehydrogenase shows a visible absorption spectrum of the cytochrome c type having an asymmetrical α-peak.

Methods for distinguishing gram-positive from gram-negative bacteria.

Abstract: Lysis by KOH and hydrolysis of L-alanine-4-nitroanilide were compared with the Gram reaction of aerobic, microaerophilic, and anaerobic bacteria. Both tests correlated well with the Gram reaction with nonfermentative bacilli and Bacillus species, whereas they did not correlate with nonsporulating anaerobes. Only campylobacteria were KOH positive and L-alanine-4-nitroanilide and gram negative.

Characterization of rat cecum cellulolytic bacteria

Abstract: Cellulose-degrading bacteria previously isolated from the ceca of rats have been characterized and identified. The most commonly isolated type was rods identified as Bacteroides succinogenes. These bacteria fermented only cellulose (e.g., pebble-milled Whatman no. 1 filter paper), cellobiose, and in 43 of 47 strains, glucose, with succinic and acetic acids as the major products. The only organic growth factors found to be required by selected strains were p-aminobenzoic acid, cyanocobalamine, thiamine, and a straight-chain and a branched-chain volatile fatty acid. These vitamin requirements differ from those of rumen strains of B. succinogenes, indicating the rat strains may form a distinct subgroup within the species. The mole percent guanine plus cytosine was 45%, a value lower than those (48 to 51%) found for three rumen strains of B. succinogenes included in this study. Cellulolytic cocci were isolated less frequently than the rods and were identified as Rumminococcus flavefaciens. Most strains fermented only cellulose and cellobiose, and their major fermentation products were also succinic and acetic acids. Their required growth factors were not identified but were supplied by rumen fluid.