Proteases production by two Vibrio species on residuals marine media

A comparative study was carried out on the growth and production of alkaline proteases by two Vibrio species using different marine peptones from fish viscera residues. The bacteria tested, Vibrio anguillarum and Vibrio splendidus, are producers of high levels of proteolytic enzymes which act as factors of virulence in fish cultures, causing high mortality rates. The kinetic assays and subsequent comparison with the parameters obtained from the adjustment to various mathematical models, highlighted the potential interest of the media formulated, for their possible production on an industrial scale, particularly the production of proteases by V. anguillarum growing in rainbow trout and squid peptones.     

Survival of Lactic Acid Bacteria in Seawater: A Factorial Study

A feasibility study of lactic bacteria as potential probiotics in larval cultures of marine fish was performed by investigating the survival of five strains of lactic bacteria in seawater by readily standardized procedures at different temperatures and salinities. These conditions were chosen in such a way that their combinations define a complete first-order factorial design. Depending on the strain and the ambient conditions, the survival adhered to first-order kinetics in some cases, and to the Gompertz equation in others. The half lives (t _0.5) calculated from these models were subsequently introduced as responses to the factorial designs, estimating the coefficients of empirical equations that describe the group effect of temperature and salinity on t _0.5. Simply additive effects were found in two cases, a negative first-order interaction in another case, while another two required second-order models.     

Temperature-dependent differences in community structure of bacteria involved in degradation of petroleum hydrocarbons under sulfate-reducing conditions

Aim: The aim of this study was to characterize the microbial community involved in anaerobic degradation of petroleum hydrocarbon under low‐ and moderate‐temperature conditions. Methods and Results: Sulfate‐reducing enrichment cultures growing on crude oil and p‐xylene were established at low and moderate temperatures. Bacterial community structures of the cultures were characterized by 16S rRNA gene‐based analysis and organisms responsible for degradation of p‐xylene were investigated by analysis of the bamA gene, involved in anaerobic degradation of aromatic compounds. The PCR‐denaturing gradient gel electrophoresis analysis indicated significant differences in microbial community structures among the cultures, depending on the temperatures of incubation. Difference depending on the temperatures was also observed in the cloning analysis of the bamA gene performed on the p‐xylene‐degrading enrichment cultures. Majority of clones detected in the culture of moderate temperature were related to Desulfosarcina ovata, whereas more diverse bamA gene sequences were obtained from the culture incubated at low temperature. Conclusions: Temperature‐dependent differences in microbial community were demonstrated by the analyses of two genes. It was suggested that sulfate‐reducing bacteria of phylogenetically different groups might be involved in the degradation of petroleum hydrocarbons in different temperature environments. Significance and Impact of the Study: This study is the first report of p‐xylene‐degrading sulfate‐reducing enrichment culture at low temperature. The results of the experiments at low temperature were distinctly different from those reported in previous studies performed at moderate temperatures.     

Variations dans ľexpression du pouvoir oncogène d'Agrobacterium tumefaciens

Variations in the expression of the oncogenic power of Agrobacterium tumefaciens due to interactions between bacteria. The effects of the virulent strain A6 of Agrobacterium tumefaciens after co-culture with non-virulent variants of the same bacterium, or even with other bacterial species (e.g. Escherichia coli), showed that interactions between different strains of bacteria exist. These interactions are expressed as a phenomenon of either enhancement or inhibition, as shown by an increase or a decrease in the weights of tumors induced in decapitated stems of Pisum sativum L. cv. Annonay. These two phenomena depend on the contact time between the bacteria in mixed cultures (type I). With a short contact time between the two bacterial types (one or two generations), infections in decapitated pea stems produced by mixed inocula caused an increase in tumor weight compared with infections induced by inocula of virulent bacteria only. If the contact time was increased to the end of the log phase, a decrease in tumor weight was observed. Clarified supernatant fluids of spent media were also used as culture media (type II) for the virulent A6 bacteria. The stimulatory or inhibitory activity of (a) substance(s) present in these supernatant fluids depended on two variables: culture time of the bacteria A6 in the supernatant fluids and the “age” of the bacterial culture used to prepare them. Weight increase of the tumors was obtained if the proliferating time of the A6 bacteria in the supernatant fluids was short (4 h), or if the super natants were obtained from “young” cultures. Inhibition of the tumor expression occurred if the contact time of A6 bacteria in the supernatant fluids was increased or if the supernatants originated from bacterial cultures at the end of their growth. The in vitro interactions between the two bacterial strains in a mixed culture (type I or type II) were suppressed in the presence of pancreatic ribonuclease. Deoxyribonuclease had no effect. This provides indirect evidence for the action of a ribonucleic acid in the expression of the oncogenic power of a bacterial population of Agrobacterium tumefaciens.     

Continuous microbial leaching of a pyritic concentrate by Leptospirillum-like bacteria

Summary Continuous leaching of a pyritic flotation concentrate by mixed cultures of acidophilic bacteria was studied in a laboratory scale airlift reactor. Enrichment cultures adapted to the flotation concentrate contained Thiobacillus ferrooxidans and Thiobacillus thiooxidans. During the late stationary growth phase of these thiobacilli growth of Leptospirillum-like bacteria was observed, too. In discontinuous cultivation no significant influence of Leptospirillum-like bacteria on leaching rates could be detected. During continuous leaching at pH 1.5 Leptospirillum-like bacteria displaced Thiobacillus ferrooxidans. The iron leaching rate achieved by Leptospirillum-rich cultures was found to be up to 3.9 times higher than that by Leptospirillum-free cultures.     

Inter-specific Interactions Between Carbon-limited Soil Bacteria Affect Behavior and Gene Expression

Recent publications indicate that inter-specific interactions between soil bacteria may strongly affect the behavior of the strains involved, e.g., by increased production of antibiotics or extracellular enzymes. This may point at an enhanced competitive ability due to inter-specific triggering of gene expression. However, it is not known if such inter-specific interactions also occur during competition for carbon which is the normal situation in soil. Here, we report on competitive interactions between two taxonomically non-related bacterial strains, Pseudomonas sp. A21 and Pedobacter sp. V48, that were isolated from a dune soil. The strains showed strong effects on each other’s behavior and gene expression patterns when growing together under carbon-limited conditions on agar. The most pronounced observed visual changes in mixed cultures as compared to monocultures were (1) strong inhibition of a bioindicator fungus, suggesting the production of a broad-spectrum antibiotic, and (2) the occurrence of gliding-like movement of Pedobacter cells. Two independent techniques, namely random arbitrary primed-PCR (RAP-PCR) and suppressive subtractive hybridization (SSH), identified in total 24 genes that had higher expression in mixed cultures compared to monocultures. Microbial interactions were clearly bidirectional, as differentially expressed genes were detected for both bacteria in mixed cultures. Sequence analysis of the differentially expressed genes indicated that several of them were most related to genes involved in motility and chemotaxis, secondary metabolite production and two-component signal transduction systems. The gene expression patterns suggest an interference competition strategy by the Pseudomonas strain and an escape/explorative strategy by the Pedobacter strain during confrontation with each other. Our results show that the bacterial strains can distinguish between intra- and inter-specific carbon competition.     

The microbiome associated with two Synechococcus ribotypes at different levels of ecological interaction

Planktonic cyanobacteria belonging to the genus Synechococcus are ubiquitously distributed in marine and fresh waters, substantially contributing to total carbon fixation on a global scale. While their ecological relevance is acknowledged, increasing resolution in molecular techniques allows disentangling cyanobacteria's role at the micro‐scale, where complex microbial interactions may drive the overall community assembly. The interplay between phylogenetically different Synechococcus clades and their associated bacterial communities can affect their ecological fate and susceptibility to protistan predation. In this study, we experimentally promoted different levels of ecological interaction by mixing two Synechococcus ribotypes (MW101C3 and LL) and their associated bacteria, with and without a nanoflagellate grazer (Poterioochromonas sp.) in laboratory cultures. The beta‐diversity of the Synechococcus‐associated microbiome in laboratory cultures indicated that the presence of the LL ribotype was the main factor determining community composition changes (41% of total variance), and prevailed over the effect of protistan predation (18% of total variance). Our outcomes also showed that species coexistence and predation may promote microbial diversity, thus highlighting the underrated ecological relevance of such micro‐scale factors.     

BACTERIAL INFLUENCE UPON GROWTH AND HYDROCARBON PRODUCTION OF THE GREEN ALGA BOTRYOCOCCUS BRAUNII1

Batch cultures of the hydrocarbon-rich alga Botryococcus braunii, Kütz. (axenic strains, non-axenic strains, associations with selected microorganisms) were examined with regard to total biomass and hydrocarbons at the onset of the stationary phase. Pronounced variations, related to the origin of the strains and to growth conditions, were observed with axenic cultures. It also appeared that the presence of microorganisms is not essential for high hydrocarbon production. Nevertheless, numerous bacteria were shown to exert considerable influence, antagonistic or beneficial, on B. braunii growth yield and hydrocarbon production. Such effects were strongly dependent on the species involved and on culture conditions. The presence of various microorganisms can influence not only the quantity of hydrocarbons produced, but also their level in the algal biomass and their relative abundance. However, their chemical structure is not affected. Intricate relationships were observed in B. braunii-bacteria systems and numerous factors (including, in some cultures, large positive effects due to bacterially produced CO₂) were implicated. Accordingly, specific associations should provide appropriate conditions for renewable hydrocarbon production via B. braunii large scale cultures.     

Monoxenic culture of the anaerobic ciliate Trimyema compressum Lackey

Sapropelic ciliates from anoxic mud samples were enriched and cultivated in monoculture together with natural food bacteria growing on cellulose. The ciliates lacked cytochrome oxidase and contained bluish fluorescent endosymbionts. One of the anaerobic ciliates, Trimyema compressum, contained methanogenic bacteria as was shown by methane formation. During continued cultivation, T. compressum gradually lost its endosymbionts. With SEM microscopy no episymbiotic bacteria could be detected.From enrichment cultures of T. compressum, anaerobic bacteria were isolated in pure culture. One of the strains, a Bacteroides spec., proved capable of serving as food bacteria, thus allowing establishment of monoxenic T. compressum cultures. These cultures exhibited a requirement for sterols as growth factors. The doubling time of this ciliate was 13 h at 28°C. The highest yield obtained was 2100 cells/ml.Dedicated to Holger W. Jannasch on the occasion of his 60th birthday     

The effect of different conditions of temperature and acidity on antimicrobial metabolites of Streptomyces sp. isolates C-11 and C-26 against F. subglutinans

In this study, the effects of pH and temperature on active two Streptomyces sp. against F. subglutinans were investigated. Streptomyces sp. isolates C-11 and C-26 were grown in submerged cultures for determination of growth curve and preparation of crude extract for further biological characterisations. Activity reached maximum at 9 and 4?days in rotary cultures for isolates C-26 and C-11, respectively. The results effects of different pH and temperature showed that these isolates were tolerant to high temperatures and the most antagonistic effects on fungi are investigated in alkaline conditions.     

Growth regulation in Neurospora crassa effects of nutrients and of temperature

Summary Mycelia of Neurospora crassa growing with quite different rates at a given temperature (30°C) are obtained by changing the composition of the culture medium: for instance a duplication time of 220 min is found when cultures are growing in Vogel's minimal medium supplemented with glycerol and one of 80 min when cultures are growing in Vogel's minimal medium supplemented with sucrose and casein hydrolysate. The kinetics of shifth-down and shift-up transitions of growth between culture conditions supporting different rates of growth are described. Temperatures above 40°C and below 20°C severely restrict growth in Vogel's minimal medium supplemented with sucrose. The Arrhenius plot of the constant of the rate of growth suggests that an inactivation process occurs at low temperatures: the molecular basis for such a process is discussed.Abbreviations used A₄₅₀ absorbance at 450 mm     

Climatic severity and the response to temperature elevation of Arctic aphids

• 1 Theory suggests that any given rise in temperature resulting from climate change will have its greatest effect on high Arctic ecosystems where growing seasons are short and temperatures low.
• 2 A small temperature rise, similar to that predicted for the middle of the next century, has profound effects on a population of the high Arctic, Dryas-feeding aphid Acyrthosiphon svalbardicum on Spitsbergen (Strathdee et al. 1993a).
• 3 Here comparative experiments on a closely related Dryas-feeding species, A. brevicorne, at two contrasting sub-Arctic sites are described. Together with the results from Spitsbergen these sites represent two colder sites (high Arctic and upland sub-Arctic) and one warmer site (lowland sub-Arctic).
• 4 Differential responses in aphid population density and overwintering egg production to temperature elevation support the hypothesis that the ecological effects are greatest at sites with the most severe climates; however, there is no similar gradient in advancement of host plant phenology with warming.

     

Digest: Structuring interactions in Streptomyces*

For bacteria growing in colonies, spatial structure can allow maintenance of costly traits such as the production of antibiotics. Using spatially structured environments, Westhoff et al. examined the benefits of streptomycin production for the bacterium Streptomyces griseus in competition with a streptomycin-susceptible strain. Streptomyces griseus outcompeted susceptible competitors, but the benefit of its antibiotic decreased as competitor resistance to streptomycin increased. Spatial structure also increased the ability of S. griseus to invade susceptible competitor populations from low starting densities. These results demonstrate that spatially structured environments can both provide and amplify benefits of antibiotics to antibiotic-producing bacteria on a microbial scale.     

Studies on Enzymatic Production of ATP

A study of the microflora of radurized Vienna sausages which did not contain preservatives revealed gram-negative diplococci and paired short rods. These radio-resistant isolates were the main residual flora in radurized viennas. The cultures were aerobic, oxidase positive and non-motile, and sugars were oxidized or not attacked at all. The population at the low temperature incubation from 0 to 10°C was abundant and these isolates may be psychrophilic bacteria. The cultures are also capable of growing in media supplemented with 7.5% sodium chloride. The present study has demonstrated that all of these organisms should be tentatively classified as an Intermediate type of Moraxella and Acinetobacter.

D₁₀ values of typical isolates ranged from 44 to 54 krad when irradiated in 0.067 m phosphate buffer, pH 7.0, and were about 4 times larger than that of Acinetobacter calcoaceticus.     

Microbiological Studies of Phytopathogenic Bacteria

During investigations on the catabolism of carbohydrate by the bacteria of the genus Erwinia, it was found that a large amount of 2-ketogluconic acid was aerobically produced from glucose by several strains of the Erwinia amylovora group of bacteria, while no production of 5-ketogluconic acid was ascertained in their growing cultures.     

Allocation of photoassimilated carbon into major algal metabolite fractions: Variation between two diatom species isolated from the Weddell Sea (Antarctica)

Distribution of photoassimilated carbon into major metabolite classes differed between two Antarctic diatom species, Nitzschia curta and a small unicellular Chaetoceros sp.. Time course uptake studies (over 54 h) revealed that ¹⁴C allocation appeared to be equilibrated after approximately 8 h at light saturated photosynthesis. During short term dark periods (6 h), polysaccharides as well as low-molecular-weight compounds were catabolised to sustain protein synthesis in the dark, whilst lipid reserves were not mobilised for this process. Experiments with these two species were conducted at 0 and -1.5°C, although no difference in the distribution of radiolabel was measured between the two temperatures. It is hypothesised that under near-optimal conditions fast growing species are characterised by a high carbon turnover associated with a rapid flow of newly assimilated carbon into polymeric compound classes. On the other hand, slower growing species (such as N. curta) may store a significant amount of surplus carbon in the low-molecular-weight metabolite fraction. Species specific preferences were observed when comparing the accumulation of radiolabel into the lipid pools.     

Mycobacterium tuberculosis Is Resistant to Isoniazid at a Slow Growth Rate by Single Nucleotide Polymorphisms in katG Codon Ser315

An important aim for improving TB treatment is to shorten the period of antibiotic therapy without increasing relapse rates or encouraging the development of antibiotic-resistant strains. In any M. tuberculosis population there is a proportion of bacteria that are drug-tolerant; this might be because of pre-existing populations of slow growing/non replicating bacteria that are protected from antibiotic action due to the expression of a phenotype that limits drug activity. We addressed this question by observing populations of either slow growing (constant 69.3h mean generation time) or fast growing bacilli (constant 23.1h mean generation time) in their response to the effects of isoniazid exposure, using controlled and defined growth in chemostats. Phenotypic differences were detected between the populations at the two growth rates including expression of efflux mechanisms and the involvement of antisense RNA/small RNA in the regulation of a drug-tolerant phenotype, which has not been explored previously for M. tuberculosis. Genotypic analyses showed that slow growing bacilli develop resistance to isoniazid through mutations specifically in katG codon Ser³¹⁵ which are present in approximately 50–90% of all isoniazid-resistant clinical isolates. The fast growing bacilli persisted as a mixed population with katG mutations distributed throughout the gene. Mutations in katG codon Ser³¹⁵ appear to have a fitness cost in vitro and particularly in fast growing cultures. Our results suggest a requirement for functional katG-encoded catalase-peroxide in the slow growers but not the fast-growing bacteria, which may explain why katG codon Ser³¹⁵ mutations are favoured in the slow growing cultures.     

TAXONOMIC CONFUSION CONCERNING CERTAIN FILAMENTOUS BLUE-GREEN ALGAE1

Throughout a long history many filamentous bacteria may have been identified in natural collections as blue-green algae. This problem has been especially acute regarding the thermophilic species of hot springs, especially at the higher temperatures. It is suggested that in the absence of pure cultures, the minimal criteria for distinguishing filamentous bacteria from blue-green algae microscopically should be: (1) observation of the chlorophyll fluorescence with a fluorescent microscope and (2) demonstration of light-dependent ¹⁴CO₂ fixation autoradiographically. Pure cultures of a number of filamentous thermophiles have been obtained from habitats at temperatures above 60 C. These cultures resemble microscopically the natural material, grow only heterot rophically, and do not contain chlorophyll.     

Coping with inadvertent lysis of Escherichia coli cultures: Strains resistant to lysogeny and infection by the stealthy lysogenic phage Φ80

Phage Φ80 can infect Escherichia coli in a stealthy manner and persist by forming lysogens. Such Φ80 lysogens are fairly common and often go undetected unless the host is grown at temperatures below 37°C. Since low growth temperatures are required for growing temperature-sensitive mutants and often preferred for large-scale applications such as protein production, Φ80-resistant strains would be useful. We report the construction of E. coli strains that cannot be efficiently lysogenized or infected by bacteriophage Φ80. These strains contain combinations of deletions or mutations in the bacterial attachment site for Φ80 integration and/or deletions in the genes required for phage absorption to the host outer membrane. These strains should help contain and prevent Φ80 infection of E. coli cultures in a laboratory or industrial setting.     

GROWTH AND EXCRETION IN PLANKTONIC ALGAE AND BACTERIA1

In short-term experiments using cultures of Chlorella pyrenoidosa, Anabaena flos-aquae, Asterionella formosa, and Navicula pelliculosa, both the proportion of photosynthetic products released from cells and the composition of these products altered, with age. In the first 3 species, percentage extracellular release values increased with increasing growth rates but the reverse trend was shown by Navicula. Fractionation of filtrates using Sephadex indicated that, in general, larger molecular weight compounds became predominant as cultures aged. Also a time-dependent shift in a similar direction occurred in cultures of all ages. In several lakes a predominance of large molecular weight compounds was apparent in filtrates even from short-term experiments. Filtrates of mixed cultures of planktonic bacteria growing on ¹⁴C glycolate were found to contain, large molecular weight organic compounds. It was demonstrated that in nonaxenic cultures of algae and in lake water, bacteria utilize low molecular weight extracellular metabolites of algal origin and larger molecular weight compounds are formed.