Showing papers in "Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology in 1984"
TL;DR: It is concluded that the denitrification systems of some bacteria are inhibited by oxygen, other species are capable of aerobicDenitrification, or co-respiration of nitrate and oxygen, and possible mechanisms and ecological implications are discussed.
Abstract: The evidence concerning aerobic denitrification over the past 100 years has been reviewed and the conclusion reached that the denitrification systems of some bacteria are inhibited by oxygen, other species are capable of aerobic denitrification, or co-respiration of nitrate and oxygen. Possible mechanisms and ecological implications are discussed.
149 citations
TL;DR: It is proposed that ability to assimilate nitrate, the sole distinction betweenHansenula andPichia, is of insufficient taxonomic value for the reliable separation of either species or genera.
Abstract: The relationship between the genera Hansenula and Pichia was examined through comparisons of DNA relatedness among phenotypically similar species. Hansenula minuta and Pichia lindneri showed 75% DNA base sequence complementarity. In other comparisons, H. nonfermentans was found to share nearly 50% of its DNA sequences with both H. minuta and P. lindneri. Because of the high degree of relatedness observed, it is proposed that ability to assimilate nitrate, the sole distinction between Hansenula and Pichia, is of insufficient taxonomic value for the reliable separation of either species or genera. Hat-spored species of Hansenula H. et P. Sydow 1919 are being transferred to Pichia Hansen 1904. Species of Hansenula and Pichia with Saturn-shaped ascospores will be transferred to the genus Williopsis.
134 citations
TL;DR: A new yeast species, Trichosporon adeninovorans, was isolated from soil by the enrichment culture method and low activities of adenine amidohydrolase and xanthine dehydrogenase were demonstrated.
Abstract: A new yeast species, Trichosporon adeninovorans, was isolated from soil by the enrichment culture method. Apart from adenine, the strain utilized uric acid, guanine, xanthine, hypoxanthine, 6,8-dihydroxypurine, putrescine, propylamine, butylamine, pentylamine, hexylamine and octylamine as sole source of carbon, nitrogen and energy. The structure of the cell wall of Tr. adeninovorans was ascomycetous. On the subcellular level growth on adenine or uric acid was accompanied with the development of microbodies in the cell. These cell organelles probably were the site of urate oxidase, an enzyme that, after growth on purine substrates, together with allantoinase was present at high activities. Low activities of adenine amidohydrolase and xanthine dehydrogenase were also demonstrated.
94 citations
TL;DR: A single strain of a budding bacterium was isolated from freshwater, which had a life-cycle, with a multitrichous swarmer stage, and produced a phase-dark inclusion of packed ribosomes and nuclear material.
Abstract: A single strain of a budding bacterium was isolated from freshwater. The strain had a life-cycle, with a multitrichous swarmer stage, and produced a phase-dark inclusion of packed ribosomes and nuclear material. The mol % G+C of the DNA was 64.4±1.0. A new genus,Gemmata with the type speciesGemmata obscuriglobus is proposed. The type strain is UQM 2246.
93 citations
TL;DR: The hypothesis that the Custers effect in this yeast is due to a disturbance of the redox balance, resulting from the tendency of the organism to produce acetic acid, and its inability to restore the balance by production of glycerol is supported.
Abstract: Aerobic growth of the yeast Brettanomyces intermedius CBS 1943 in batch culture on a medium containing glucose and yeast extract proceeded via a characteristic pattern. In the first phase of growth glucose was fermented to nearly equal amounts of ethanol and acetic acid. After glucose depletion, growth continued while the ethanol produced in the first phase was almost quantitatively converted to acetic acid. Finally, after a long lag phase, growth resumed with concomitant consumption of acetic acid. When the culture was made anaerobic during the first phase, growth, glucose consumption and metabolite production stopped immediately. This Custers effect (inhibition of alcoholic fermentation as a result of anaerobic conditions) was transient. After 7-8 h the culture was adapted to anaerobiosis, and growth and ethanol production resumed. The lag phase could be shortened at will by the introduction of hydrogen acceptors, such as oxygen or acetoin, into the culture. Glycerol production was not observed during any phase of growth. These results support the hypothesis that the Custers effect in this yeast is due to a disturbance of the redox balance, resulting from the tendency of the organism to produce acetic acid, and its inability to restore the balance by production of glycerol.
80 citations
TL;DR: Studies of the enzymes isolated from various sources have indicated that phosphoribulokinase is the target enzyme for the control of the rate of carbon dioxide fixation via the Calvin cycle through modulation of existing enzyme activity.
Abstract: The Calvin cycle of carbon dioxide fixation constitutes a biosynthetic pathway for the generation of (multi-carbon) intermediates of central metabolism from the one-carbon compound carbon dioxide. The product of this cycle can be used as a precursor for the synthesis of all components of cell material. Autotrophic carbon dioxide fixation is energetically expensive and it is therefore not surprising that in the various groups of autotrophic bacteria the operation of the cycle is under strict metabolic control. Synthesis of phosphoribulokinase and ribulose-1,5-bisphosphate carboxylase, the two enzymes specifically involved in the Calvin cycle, is regulated via end-product repression. In this control phosphoenolpyruvate most likely has an alarmone function. Studies of the enzymes isolated from various sources have indicated that phosphoribulokinase is the target enzyme for the control of the rate of carbon dioxide fixation via the Calvin cycle through modulation of existing enzyme activity. In general, this enzyme is strongly activated by NADH, whereas AMP and phosphoenolpyruvate are effective inhibitors. Recent studies of phosphoribulokinase in Alcaligenes eutrophus suggest that this enzyme may also be regulated via covalent modification.
50 citations
TL;DR: Criteria used are reviewed; possible stabilization of nomenclature is envisaged; further standardization of conditions of cultivation and careful description of micromorphology are necessary, before the species concepts of different laboratories can be reconciled.
Abstract: Classification of species in the three generaPenicillium, Aspergillus andFusarium is in a state of change. Criteria used are reviewed; possible stabilization of nomenclature is envisaged. Proper typification of recognized species is necessary. InPenicillium andAspergillus some species known mainly from fermented food are considered as domesticated versions of other, wild species. InPenicillium a further standardization of conditions of cultivation and careful description of micromorphology are necessary, before the species concepts of different laboratories can be reconciled. Secondary metabolites (mycotoxins, pigments) prove to support taxonomic conclusions reached by morphological work. InAspergillus the taxonomic situation is simpler than inPenicillium, but typification is not yet sufficiently settled. For some well-known species older names were recently unearthed. InFusarium the taxonomic views of different laboratories are becoming more similar, but much work on type specimens and neotypification of other species is still required. More genetic evidence is necessary to decide about specific or varietal rank in critical cases.
47 citations
TL;DR: In almost all infections in the oral cavity, mixed populations of bacteria are present, however, recent evidence points to a certain specificity in these infections:Streptococcus mutans is related to caries and black-pigmentedBacteroides species are suspected pathogens in periodontal disease.
Abstract: In almost all infections in the oral cavity, mixed populations of bacteria are present. However, recent evidence points to a certain specificity in these infections: Streptococcus mutans is related to caries and black-pigmented Bacteroides species are suspected pathogens in periodontal disease. Periodontal diseases, endodontic infections and submucous abscesses in the oral cavity are probably mixed infections in which anaerobic bacteria together with facultatives or other anaerobes are present. In experimental mixed anaerobic infections black-pigmented Bacteroides strains have been shown to play a key role. Little is known about the pathogenic synergy between the bacteria involved in mixed infections. Important mechanisms could be nutritional interrelationships and interactions with the host defense. Within the group of black-pigmented Bacteroides B. gingivalis seems to be the most virulent species. These bacteria possess a great number of virulence factors, which might be important in the pathogenesis of oral infections.
42 citations
TL;DR: The transport of malate is inhibited by uranyl ions; various other inhibitors of transport and phosphorylation were of little influence; it is assumed that the inducible protein carrier for malate operates by facilitated diffusion.
Abstract: Zygosaccharomyces bailii possesses a constitutive malic enzyme, but only small amounts of malate are decomposed when the cells ferment fructose. Cells growing anaerobically on glucose (glucose cells) decompose malate, whereas fructose cells do not. Only glucose cells show an increase in the intracellular concentration of malate when suspended in a malate-containing solution. The transport system for malate is induced by glucose, but it is repressed by fructose. The synthesis of this transport system is inhibited by cycloheximide. Of the two enantiomers L-malate is transported preferentially. The transport of malate by induced cells is not only inhibited by addition of fructose but also inactivated. This inactivation is independent of the presence of cycloheximide. The transport of malate is inhibited by uranyl ions; various other inhibitors of transport and phosphorylation were of little influence. It is assumed that the inducible protein carrier for malate operates by facilitated diffusion. Fructose cells of Z. bailii and cells of Saccharomyces cerevisiae do not contain a transport system for malate.
40 citations
TL;DR: A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.
Abstract: Three hundred and eighty three yeasts isolated from samples of unsulphited or sulphited sausages and skinless sausages and minced beef were characterized in detail.Debaryomyces hansenii was the most commonly isolated yeast from most samples followed byCandida zeylanoides andPichia membranaefaciens. The presence of sulphite in sausages did not appear to affect the numbers and range of yeasts present but did affect their relative proportions. A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.
36 citations
TL;DR: The obligate endoparasitic fungus Meria coniospora lives its entire vegetative life within infected nematodes and the infection, starting with adhesion of conidia to the nematode surface, growth of trophic hyphae, production of conidiophores and conidia, was followed using light, scanning and transmission electron microscopy.
Abstract: The obligate endoparasitic fungus Meria coniospora lives its entire vegetative life within infected nematodes. Conidia of M. coniospora infect the nematode Panagrellus redivivus mainly in the mouth region. The infection, starting with adhesion of conidia to the nematode surface, growth of trophic hyphae, production of conidiophores and conidia, was followed using light, scanning and transmission electron microscopy.
TL;DR: A new ascogenous yeast species, Dekkera anomala, is described, which differs morphologically and physiologically from the species presently accepted in the genus DekkerA by the formation of blastese and the ability to ferment lactose.
Abstract: A new ascogenous yeast species, Dekkera anomala, is described. The strains studied were isolated from spoiled soft drinks. This species differs morphologically and physiologically from the species presently accepted in the genus Dekkera by the formation of blastese and the ability to ferment lactose.
TL;DR: Selective decontamination of the gastrointestinal tract has been successfully used prophylactically in neutropenic patients but needs to be monitored bacteriologically and should perhaps be used more widely in the hospital to control development and spread of antibiotic-resistant strains.
Abstract: The colonization resistance (CR) of the gastrointestinal tract to potential pathogens depends partly on factors within the host but to a greater extent on the normal (anaerobic) gut flora. Its strength varies between individuals. These individual differences in resistance to colonization by pathogenic microorganisms may explain differences in susceptibility to infection. CR is lowered by remission-inducing treatment (radiation and/or chemotherapy) in leukaemia, but more severely by certain antibiotics. Development (by selection or transfer) of resistance to these antibiotics may lead to overgrowth and penetration of the mucosal lining by the overgrowing (potentially) pathogenic bacteria. Other antibiotics however, if sufficiently dosed, have been found to eliminate (potential) pathogens selectively without decreasing CR. This selective decontamination of the gastrointestinal tract has been successfully used prophylactically in neutropenic patients but needs to be monitored bacteriologically. It should perhaps be used more widely in the hospital to control development and spread of antibiotic-resistant strains.
TL;DR: Current insights on classification, bacteriology, pathogenic potential and virulence factors, as well as the main features of the clinical syndromes in which coagulase-negative staphylococci are involved are reviewed.
Abstract: In contrast to the well-established pathogenStaphylococcus aureus, the coagulase-negative staphylococci, formerly collectively calledS. epidermidis, were until recently regarded as harmless commensals. During the last two decades, however, the coagulase-negative staphylococci have clearly emerged as pathogens in patients carrying artificial devices, such as prosthetic heart valves, hip prostheses and cerebrospinal fluid shunts, and in patients with compromised host defenses such as premature neonates and cancer and transplant patients.
TL;DR: Improvements in hygiene and measures taken to limit multiplication of microorganisms in the dry area of the production lines resulted in reduction of both numbers of Enterobacteriaceae in environmental samples and frequency of their occurrence in finished products.
Abstract: Finished products and samples from the environment of the production line in rendering plants were checked for Enterobacteriaceae and salmonellae. Improvements in hygiene and measures taken to limit multiplication of microorganisms in the dry area of the production lines resulted in reduction of both numbers of Enterobacteriaceae in environmental samples and frequency of their occurrence in finished products. Simultaneously, there was an equivalent reduction of salmonellae positives in environmental samples and finished products. Consequently, the determination of Enterobacteriaceae can be used as an effective tool to assess the improvements in good manufacturing practices.
TL;DR: The nuclear DNa of 28 species (30 strains investigated) of yeasts classified currently or previously in the genus Trichosporon was analysed for its molar percentage of guanine + cytosine (mol% G+C) and suggested the separation of the organisms studied into two groups.
Abstract: The nuclear DNa of 28 species (30 strains investigated) of yeasts classified currently or previously in the genus Trichosporon. was analysed for its molar percentage of guanine + cytosine (mol% G+C). This criterion, together with biochemical characteristics, suggested the separation of the organisms studied into two groups. The first group, which appears related to the Ascomycetes, includes thirteen species with a G+C content lower than 50 mol% (34.7−48.8), and lacks urease (except T. margaritiferum). The second group appears related to the Basidiomycetes and includes fifteen species with a G+C content higher than 50 mol% (57−64) and has the ability to hydrolyse urea.
TL;DR: Arguments are given for the hypothesis that co-evolution has taken place through mutual interaction of host plants and indigenousRhizobium andFrankia populations in the soil leading to most efficient symbiotic associations.
Abstract: A description is given of the natural variation in nitrogen-fixingRhizobium andFrankia spp. strains and the ability to form root nodules on compatible host plants. Arguments are given for the hypothesis that co-evolution has taken place through mutual interaction of host plants and indigenousRhizobium andFrankia populations in the soil leading to most efficient symbiotic associations. The significance of root nodules as selective enrichment cultures of particular strains in natural and cultivated soils is exemplified byRhizobium leguminosarum on various ecotypes ofPisum sativum and withFrankia sp. on various actinorhizal plants, in particularAlnus spp., in different geographic regions. The importance of a host-dependent distribution ofRhizobium andFrankia spp. for agriculture and forestry is discussed.
TL;DR: By measuring molar growth yields it has been demonstrated that carbon-limited, nitrogen-fixing cultures obtain additional ATP from hydrogen oxidation, and that site 2 of oxidative phosphorylation is passed during hydrogen oxidation.
Abstract: In this survey we describe the influence of hydrogen oxidation on the physiology ofRhizobium ORS 571. The presence of hydrogen is required for the synthesis of hydrogenase. Carbon substrates do not repress the synthesis of hydrogenase. The respiratory system contains cytrochromes of theb- andc-type. Cytochromea600 is present after growth at high oxygen tensions. The nature of the terminal oxidases functioning at low oxygen tensions has not been established yet. → H+/O values with endogenous substrates are between 6 and 7. The results show the presence of two phosphorylation sites: site 1 (ATP/2e=1.0) and site 2(ATP/2e=1.33). By measuring molar growth yields it has been demonstrated that carbon-limited, nitrogen-fixing cultures obtain additional ATP from hydrogen oxidation, and that site 2 of oxidative phosphorylation is passed during hydrogen oxidation. A method is described to calculate ATP/N2 values (the total amount of ATP used by nitrogenase during the fixation of 1 mol N2) and H2/N2 ratios (mol hydrogen formed per mol N2 fixed) in aerobic organisms. ForRhizobium ORS 571 the ATP/N2 value is about 40 and the H2/N2 ratio is between 5 and 7.5. Cells obtained from oxygen-limited nitrogen-fixing cultures contain 30–40% poly-β-hydroxybutyrate, which explains the high molar growth yields found. Hydrogen has not been detected in the effluent gas of these cultures, which may point to reoxidation of the hydrogen formed at nitrogen fixation. Calculations show that the effect of hydrogen reoxidation on the efficiency of nitrogen fixation (g N fixed × mol−1 substrate converted) is not very large and that the actual H2/N2 ratio is of much more importance.
TL;DR: Detailed NM R studies showed that methanopterin from M. thermoautotrophicum contains ribitol, ribose-5-phosphate, a glutarate derivative, a pterin substituted at the C 6and C7-positions and a second chromophore, which is probably an aniline derivative.
Abstract: Methanopterin is probably the first coenzyme involved in the reduction of CO 2 to CH 4 by Methanobacterium thermoautotrophicum. It is reduced and labelled with 14C02 in whole cells (Daniels and Zeikus, 1978; Keltjens et al., 1982) and it stimulates the formation of CH 4 in resolved cell-free extracts (J. Leigh, personal communication). We developed a quantitative, anaerobic and non-destructive method to measure the conversion of methanopterin in cell-free extracts with reversed-phase HPLC and a gradient of 0-25% methanol in 25 mM acetate buffer (pH 6.0). The conversion of methanopterin and the production of methane proceeded under identical conditions and required the presence of Mg 2+ plus ATP, hydrogen and methylcoenzyme M. The main products formed during the enzymatic conversion of methanopterin were two reduced pterins, which had lost the major part of the side chain of methanopterin, the side chain itself and a fourth unidentified reaction product. Chemical reduction of methanopterin with H 2 and a Pd/C catalyst yielded the same products as found with the enzymatic conversion, except for the fourth reaction product. Methanopterin and a number of degradation products were purified and analysed. Detailed NM R studies showed that methanopterin from M. thermoautotrophicum contains ribitol, ribose-5-phosphate, a glutarate derivative, a pterin substituted at the C 6and C7-positions and a second chromophore, which is probably an aniline derivative.
TL;DR: Some aspects of the bacteriology of aerobic and anaerobic waste water purification are discussed in view of current opinions and recent developments in the technology of waste water treatment.
Abstract: Some aspects of the bacteriology of aerobic and anaerobic waste water purification are discussed in view of current opinions and recent developments in the technology of waste water treatment. Various contributions of scientific workers attached to the Department of Microbiology of the Agricultural University, Wageningen, during the past 65 years are summarized. Besides, present investigations are described and research activities in future indicated.
TL;DR: An undescribed yeast species was recovered from oriental and yellow mustard seeds and most closely resembled Nematospora coryli but its asci were rarely cylindrical and its spores did not possess a whip-like appendage.
Abstract: An undescribed yeast species was recovered from oriental (Brassica juncea) and yellow (B. hirta) mustard seeds. The new species most closely resembled Nematospora coryli but its asci were rarely cylindrical. The asci and ascospores of N. sinecauda were smaller and the spores did not possess a whip-like appendage. During germination a sprout cell formed first on the smooth anterior surface of the spore above the median ridge. The posterior region of the spore was decorated with interrupted concentric ridges. A description of the new species is given.
TL;DR: The development of today’s penicillin production technology is analysed in terms of changes in the quality and intensity of the production process.
Abstract: A brief description is given of the history of penicillin production in the Netherlands. The development of today's penicillin production technology is analysed in terms of changes in the quality and intensity of the production process. Technological as well as genetical developments are shown to be of influence on the quality and the intensity of the production process. The analysis is illustrated by a brief description of the productivity improvement of the penicillin fermentation as it occurred at Gist-brocades during the past 20 years.
TL;DR: Germ tube and subsequent mycelial development from yeast-like and swollen cells of Aureobasidium pullulans (IMI 45533) was induced by yeast extract in defined liquid medium and the progeny of mycelium and future generations were unaffected by yeast Extract.
Abstract: Germ tube and subsequent mycelial development from yeast-like and swollen cells of Aureobasidium pullulans (IMI 45533) was induced by yeast extract in defined liquid medium. This morphogenetic transition was dependent on inoculum size; pH effects were not involved and once mycelial development was induced in the cells it continued even in the absence of yeast extract. The progeny of mycelium and future generations were unaffected by yeast extract. Cessation of germination was not due to any obvious medium changes but appeared to be partly due to the production of a germination inhibitor, which could also be produced by control cells grown in the absence of yeast extract.
TL;DR: FiveAcetobacter isolates from lactic acid fermented meat food for pets were characterized by 177 morphological, physiological and biochemical traits and it is emphasized that access of such bacteria to lactic Acid fermented foods should be avoided.
Abstract: FiveAcetobacter isolates from lactic acid fermented meat food for pets were characterized by 177 morphological, physiological and biochemical traits. Four isolates were identified asA. pasteurianus, one asA. aceti. It is emphasized that access of such bacteria to lactic acid fermented foods should be avoided.
TL;DR: The preliminary data suggest that B. fragilis is itself poorly chemotactic and reduces the chemoattractivity of Proteus mirabilis, which is surprising when it is considered that abscess formation is the hall-mark of B.Fragilis infections and needs clarification.
Abstract: In this article we review our researches into the pathogenesis of mixed infections. These may conveniently be divided into in vitro and in vivo studies. In vitro we confirmed that interference with the killing of aerobes by polymorphonuclear leucocytes (PMN’s) is a property of theBacteroides strains tested and appears to depend on competition for opsonins i.e. complement factors. Further studies are in progress to define which complement factors and which bacterial structures are involved. The influence ofB. fragilis on chemotaxis has also been studied. Our preliminary data suggest thatB. fragilis is itself poorly chemotactic and reduces the chemoattractivity ofProteus mirabilis. This observation is surprising when we consider that abscess formation is the hall-mark ofB. fragilis infections and needs clarification. In vivo we have developed a skin infection model in mice which is economical and gives reproducible and quantitative results. In this model we have demonstrated pathogenic synergy betweenEscherichia coli andB. fragilis. Further studies are planned to assess the role of complement and bacterial factors in this in vivo synergy.
TL;DR: A clear correlation was observed between the yield values (of both glucose- and K+-limited cultures) and the steady state concentration of CO2 in the effluent gas and it is suggested that dissolved CO2 exerts an effect on both metabolism and the energetics of cell synthesis.
Abstract: Progressively increasing the input concentration of growth-limiting nutrient (glucose, ammonia, K+) to anaerobic chemostat cultures ofKlebsiella aerogenes (D=0.38 h−1; 35°C; pH 6.8) led to a non-linear increase in bacterial cell concentration. At modest population densities, residual growth-limiting substrate levels increased substantially, with increasing input concentration, and the culture bacterial dry weight tended to a constant value. With the glucose-limited culture, increasing the glucose input concentration above 20 g·1−1 led to accumulation of unused glucose and a change in the fermentation pattern. There was a concomitant lowering of the yield value with respect to glucose consumption, and the calculated YATP value similarly declined. Addition of extra essential (non-limiting) nutrients to the culture was without effect. Similarly, addition of individual fermentation products (acetate, ethanol,d-lactate, 2,3-butanediol, succinate) to the feed medium, in varying concentrations and in different combinations, failed to influence the fermentation pattern or the energetics of cell synthesis. However, a clear correlation was observed between the yield values (of both glucose- and K+-limited cultures) and the steady state concentration of CO2 in the effluent gas. Increasing the concentration CO2 either by increasing the population density or lowering the sparging rate of nitrogen gas through the culture, effected a lowering of the yield values. It is suggested that dissolved CO2 exerts an effect on both metabolism and the energetics of cell synthesis. A possible mechanism of energy dissipation (i.e., a futile cycle) involving carboxylation and decarboxylation reactions is proposed.
TL;DR: The state of the art of hybridoma technology is reviewed with emphasis on the results obtained by antibody engineering in laboratories for the development of monoclonal antibodies for specific use in diagnostic tests.
Abstract: Antibody engineering is the selection process enabling the isolation of hybridoma clones, each of which produces an antibody with predefined qualities. The state of the art of hybridoma technology is reviewed with emphasis on the results obtained by antibody engineering in our laboratories for the development of monoclonal antibodies for specific use in diagnostic tests. The perspective for in vitro monoclonal antibody production as well as the application of monoclonal antibodies for diagnostic reagents, industrial purification and therapeutic use are indicated.
TL;DR: The human-pathogenic fungus, Phialophora cyanescens sp.
Abstract: The human-pathogenic fungus, Phialophora cyanescens sp. nov. is characterized by the abundant production of chlamydospore-like cell aggregates resembling the form-genus Phaeosclera Sigler et al., and by elongate phialides with ellipsoidal conidia. A brown pigment and a blue, acid-labile pigment may be present.
TL;DR: The stage at which exclusion operates in matings between donors belonging to the I-type incompatibility group (IncI) was investigated and it was revealed that the exclusion by pRAH308 does not operate at the level of aggregate formation, but acts at the stage of DNA transfer.
Abstract: The stage at which exclusion operates in matings between donors belonging to the I-type incompatibility group (IncI) was investigated Mating between Escherichia coli cells harbouring the I-type plasmid R144 and E coli cells harbouring the R144-derived recombinant plasmid pRAH308, which causes a hundredfold exclusion, was performed on a membrane filter to test whether mating aggregate formation was disturbed Besides, level and kinetics of the formation of mating aggregates in mixtures of R144+ donor cells and recipient cells carrying plasmid pRAH308 (exclusion-proficient) was compared with the aggregate formation in mixtures of the donor cells and exclusion-deficient recipient cells Results from these experiments revealed that the exclusion by pRAH308 does not operate at the level of aggregate formation, but acts at the stage of DNA transfer The exclusion phenomenon by the recombinant plasmid pRAH308 appeared to be representative for exclusion caused by plasmid R144, since essentially identical results were obtained if plasmid R144 was used as exclusion-determining factor
TL;DR: Ten phages of Bacillus polymyxa were isolated from four different Brazilian soils and tests of resistance against physical and chemical agents showed that the isolates could be distributed among six different groups.
Abstract: Ten phages of Bacillus polymyxa were isolated from four different Brazilian soils. All were dsDNA-containing phages belonging to Bradley types A and B. Data obtained from electron microscopy and tests of resistance against physical and chemical agents showed that the isolates could be distributed among six different groups. Host range data were in agreement with this classification. When tested against 88 strains of 18 Bacillus species, these phages only infected B. polymyxa strains, thus revealing specificity for this species. Three phage groups lysed all 42 available B. polymyxa strains and are suggested for use in rapid identification of this species.