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PubMedDate not supplied

[Typhoid fever in Vietnam. I. Bacteriological study (607 Salmonella strains isolated from 1961 to 1975 at the Grall Hospital of Saigon)].

From 1961 to 1975, researches on salmonellosis have been carried out in Hospital Grall, in Saigon, mainly during two periods (1961-1964, then 1971-1975). 607 strains of Salmonella have been isolated for these 15 years (558 S. typhi and 49 Salmonella, among several other serotypes). As typhoid fever is most important, the authors have studied this disease very carefully. The most efficacious technique of isolating is hemoculture. With coproculture, the results are disappointing. Scarcely, some strains have been found in samples of various origins. Indirect diagnosis methods are less interesting. They may induce only a presumptive diagnosis. S. typhi is always predominant : 86,5 p. 100 from 1961 to 1964 and 96,1 p. 100 from 1972 to 1975. Diffusion of this germ during the second period is linked to the occurring of resistance to chloramphenicol. Some other serotypes are observed scarcely. The lysotypes have been determined for almost all the strains (202, then 323, during the two phases of this study). From 172 to 1975, 24 different lysotypes have been found. Lysotype I + IV is predominant (59 p. 100), but the incidence of D 6 and of 46 (6,8 p. 100) is somewhat high, if it is compared to the others. Lysotype 46 has been observed only since 1971. It has been spreading up to now in South East Asia. Stretching of this lysotype, out of its original focus, is an important epidemiological character. In 1972, resistance of S. typhi to chloramphenicol appeared and it has been increasing mostly during the following years. From 1972 to 1975, 211 strains on 288 were found resistant (highest point in 1975 : 85,4 p. 100). It was a multiresistance to 4 antibiotics (antibiotype : CTSSu). This pehnomenon of plasmidic resistance was investigated in Institut Pasteur (Paris). Many lysotypes have been involved in resistance (14 among 24). Clinical study has been realized for 189 patients. During the typical period of the disease, fever is the major symptom. More scarcely, other clinical features are observed. Various complications have been related. The evolution of the disease has been generally satisfactory, as far as mortality (less than 2 p. 100), sequelae (1 p. 100) and relapses (2 p. 100) are concerned. Clinical course has not been modified by resistance of the germs.

Anti-Bacterial Agents↗
PubMedDate not supplied

[Children typhoid fever in Saigon (Vietnam) : epidemiological and biological aspects (author's transl)].

A review of 130 children cases of typhoid fever in Saigon (Vietnam). Leuco-neutropenia is far from regular but thrombopenia is frequent. The typhoid bacillus is generally cultivated from blood during the first two weeks of the evolution. There is evidence in most S. typhi strains of a plasmid resistance for streptomycine, chloramphenicol, tetracycline and sulfamides. Strains of the various other enterobacteria of the intestinal flora are generally resistant for many more antibiotics than S. typhi.

Adolescent↗
PubMed1999

A special reactor design for investigations of mixing time effects in a scaled-down industrial L-lysine fed-batch fermentation process

A specially designed model reactor based on a 42-L laboratory fermentor was equipped with six stirrers (Rushton turbines) and five cylindrical disks. In this model reactor, the mixing time, Theta(90), turned out to be 13 times longer compared with the 42-L standard laboratory fermentor fitted with two Rushton turbines and four wall-fixed longitudinal baffles. To prove the suitability of the model reactor for scaledown studies of mixing-time-dependent processes, parallel exponential fed-batch cultivations were carried out with the leucine-auxotrophic strain, Corynebacterium glutamicum DSM 5715, serving as a microbial test system. L‐Leucine, the process-limiting substrate, was fed onto the liquid surface of both reactors. Cultivations were conducted using the same inoculum material and equal oxygen supply. The model reactor showed reduced sugar consumption (-14%), reduced ammonium consumption (-19%), and reduced biomass formation (-7%), which resulted in a decrease in L-lysine formation (-12%). These findings were reflected in less specific enzyme activity, which was determined for citrate synthase (CS), phosphoenolpyruvate carboxylase (PEP-C), and aspartate kinase (AK). The reduced specific activity of CS correlated with lower CO(2) evolution (-36%) during cultivation. The model reactor represents a valuable tool to simulate the conditions of poor mixing and inhomogeneous substrate distribution in bioreactors of industrial scale. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed1999

Post-Viking microbiology: new approaches, new data, new insights.

In the 20 years since the Viking experiments, major advances have been made in the areas of microbial systematics, microbial metabolism, microbial survival capacity, and the definition of environments on earth, suggesting that life is more versatile and tenacious than was previously appreciated. Almost all niches on earth which have available energy, and which are compatible with the chemistry of carbon-carbon bonds, are known to be inhabited by bacteria. The oldest known bacteria on earth apparently evolved soon after the formation of the planet, and are heat loving, hydrogen and/or sulfur metabolizing forms. Among the two microbial domains (kingdoms) is a great deal of metabolic diversity, with members of these forms being able to grow on almost any known energy source, organic or inorganic, and to utilize an impressive array of electron acceptors for anaerobic respiration. Both hydrothermal environments and the deep subsurface environments have been shown to support large populations of bacteria, growing on energy supplied by geothermal energy, thus isolating these ecosystems from the rest of the global biogeochemical cycles. This knowledge, coupled with new insights into the history of the solar system, allow one to speculate on possible evolution and survival of life forms on Mars.

Antarctic Regions↗
PubMed2003

Antimicrobial egg cleaning by the fringed darter (Perciformes: Percidae: Etheostoma crossopterum): implications of a novel component of parental care in fishes.

Broad-spectrum antimicrobial compounds have recently been identified in the epidermal mucus of fishes and probably serve as a first line of defence against microbial pathogens. Because of the ubiquitous nature of fungi and bacteria in aquatic systems, defence against these pathogens should be required throughout the lifespan of fishes, including the egg stage. We conducted experiments on Etheostoma crossopterum (Percidae: Catonotus), the fringed darter, to determine if the presence of a guarding male inhibits microbial colonization of eggs. Based on results from a combination of in-stream experiments, in vitro microbial assays, and morphological characteristics and behaviour of breeding males, we propose that antimicrobial egg cleaning by the guarding male is an effective component of parental care in these fish. Although innate antimicrobial compounds have been identified in a variety of organisms ranging from insects to vertebrates, integration of these compounds into a species's reproductive life history has been identified only in a small number of insect species. The results from this study not only indicate that E. crossopterum males provide a novel form of vertebrate parental care, but also have implications regarding the evolution of parental care in fishes and transitional evolutionary stages from no parental care to male parental care.

Animals↗
PubMed1994

Relative role of eukaryotic and prokaryotic microorganisms in phenanthrene transformation in coastal sediments.

THE RELATIVE ROLE OF EUKARYOTIC VERSUS PROKARYOTIC MICROORGANISMS IN PHENANTHRENE TRANSFORMATION WAS MEASURED IN SLURRIES OF COASTAL SEDIMENT BY TWO DIFFERENT APPROACHES: detection of marker metabolites and use of selective inhibitors on phenanthrene biotransformation. Phenanthrene biotransformation was measured by polar metabolite formation and CO(2) evolution from [9-C]phenanthrene. Radiolabeled metabolites were tentatively identified by high-performance liquid chromatography (HPLC) separation combined with UV/visible spectral analysis of HPLC peaks and comparison to authentic standards. Both yeasts and bacteria transformed phenanthrene in slurries of coastal sediment. Two products of phenanthrene oxidation by fungi, phenanthrene trans-3,4-dihydrodiol and 3-phenanthrol, were produced in yeast-inoculated sterile sediment. However, only products of phenanthrene oxidation typical of bacterial transformation, 1-hydroxy-2-naphthoic acid and phenanthrene cis-3,4-dihydrodiol, were isolated from slurries of coastal sediment with natural microbial populations. Phenanthrene trans-dihydrodiols or other products of fungal oxidation of phenanthrene were not detected in the slurry containing a natural microbial population. A predominant role for bacterial transformation of phenanthrene was also suggested from selective inhibitor experiments. Addition of streptomycin to slurries, at a concentration which suppressed bacterial viable counts and rates of [methyl-H]thymidine uptake, completely inhibited phenanthrene transformation. Treatment with colchicine, at a concentration which suppressed yeast viable counts, depressed phenanthrene transformation by 40%, and this was likely due to nontarget inhibition of bacterial activity. The relative contribution of eukaryotic microorganisms to phenanthrene transformation in inoculated sterile sediment was estimated to be less than 3% of the total activity. We conclude that the predominant degraders of phenanthrene in muddy coastal sediments are bacteria and not eukaryotic microorganisms.

Journal Article↗
PubMed2002

Structure and mechanism of action of a cofactor-dependent phosphoglycerate mutase homolog from Bacillus stearothermophilus with broad specificity phosphatase activity.

The crystal structure of Bacillus stearothermophilus PhoE (originally termed YhfR), a broad specificity monomeric phosphatase with a molecular mass of approximately 24 kDa, has been solved at 2.3 A resolution in order to investigate its structure and function. PhoE, already identified as a homolog of a cofactor-dependent phosphoglycerate mutase, shares with the latter an alpha/beta/alpha sandwich structure spanning, as a structural excursion, a smaller subdomain composed of two alpha-helices and one short beta-strand. The active site contains residues from both the alpha/beta/alpha sandwich and the sub-domain. With the exception of the hydrophilic catalytic machinery conserved throughout the cofactor-dependent phosphoglycerate mutase family, the active-site cleft is strikingly hydrophobic. Docking studies with two diverse, favored substrates show that 3-phosphoglycerate may bind to the catalytic core, while alpha-napthylphosphate binding also involves the hydrophobic portion of the active-site cleft. Combining a highly favorable phospho group binding site common to these substrate binding modes and data from related enzymes, a catalytic mechanism can be proposed that involves formation of a phosphohistidine intermediate on His10 and likely acid-base behavior of Glu83. Other structural factors contributing to the broad substrate specificity of PhoE can be identified. The dynamic independence of the subdomain may enable the active-site cleft to accommodate substrates of different sizes, although similar motions are present in simulations of cofactor-dependent phosphoglycerate mutases, perhaps favoring a more general functional role. A significant number of entries in protein sequence databases, particularly from unfinished microbial genomes, are more similar to PhoE than to cofactor-dependent phosphoglycerate mutases or to fructose-2,6-bisphosphatases. This PhoE structure will therefore serve as a valuable basis for inference of structural and functional characteristics of these proteins.

Amino Acid Sequence↗
PubMed2004

[Helicobacter pylori resistance to metronidazole and clarythromicin: descriptive analysis 1997-2000].

BACKGROUND AND OBJECTIVE: We aimed to assess the resistance of H. pylori to clarithromycin and metronidazole, in patients with and without previous eradication treatment, in a geographic area from the north of Spain. We also analyzed the evolution of resistance rates and its relationships with annual antibiotic consumption. PATIENTS AND METHOD: Retrospective study including all patients with H. pylori infection and positive culture from January 1997 to December 2000. Minimal inhibitory concentrations (MIC) determined by the E test were used to report the clarithromycin (MIC > 2 mg/l) and metronidazole (MIC > 32 mg/l) resistance. RESULTS: A total of 537 clinical H. pylori isolates from patients without (n = 389) and with previous eradication treatment (n = 148) were studied. H. pylori resistance to clarithromycin and metronidazole was found in 8.7% (95% CI, 6.1-12) and 13.8% (95% CI, 10.4-17.3) patients without previous eradication treatment and in 39.2% (95% CI, 31.3-47.1) and 37.8% (95% CI, 30-45.7) patients with previous eradication treatment (p < 0.001), respectively. Clarithromycin resistance remained stable (1997: 9.7%; 1998: 5.7%; 1999: 11.8%; 2000: 6.2%) whereas metronidazole resistance decreased over the 4 years study period (1997: 38.7%; 1998: 15.1%; 1999: 9%; 2000: 6.9%). We did not observe any clear relationship between resistance's evolution and antibiotic annual consumption. CONCLUSIONS: In our geographic area, primary resistance rates for clarithromycin remained stable whereas resistance for metronidazole decreased over the 4 years period.

Adult↗
PubMed2005

Predation on prokaryotes in the water column and its ecological implications.

The oxic realms of freshwater and marine environments are zones of high prokaryotic mortality. Lysis by viruses and predation by ciliated and flagellated protists result in the consumption of microbial biomass at approximately the same rate as it is produced. Protist predation can favour or suppress particular bacterial species, and the successful microbial groups in the water column are those that survive this selective grazing pressure. In turn, aquatic bacteria have developed various antipredator strategies that range from simply 'outrunning' protists to the production of highly effective cytotoxins. This ancient predator-prey system can be regarded as an evolutionary precursor of many other interactions between prokaryotic and eukaryotic organisms.

Animals↗
PubMed2004

The ecology and genetics of microbial diversity.

Natural communities of microbes are often diverse, a fact that is difficult to reconcile with the action of natural selection in simple, uniform environments. We suggest that this apparent paradox may be resolved by considering the origin and fate of diversity in an explicitly ecological context. Here, we review insights into the ecological and genetic causes of diversity that stem from experiments with microbial populations evolving in the defined conditions of the laboratory environment. These studies highlight the importance of environmental structure in governing the fate of diversity and shed light on the genetic mechanisms generating diversity. We conclude by emphasizing the importance of placing detailed molecular-level studies within the context of a sound ecological and evolutionary framework.

Bacteria↗
PubMed1992

The oldest records of photosynthesis.

There is diverse, yet controversial fossil evidence for the existence of photosynthesis 3500 million years ago. Among the most persuasive evidence is the stromatolites described from low grade metasedimentary rocks in Western Australia and South Africa. Based on the understanding of the paleobiology of stromatolites and using pertinent fossil and Recent analogs, these Early Archean stromatolites suggest that phototrophs evolved by 3500 million years ago. The evidence allows further interpretation that cyanobacteria were involved. Besides stromatolites, microbial and chemical fossils are also known from the same rock units. Some microfossils morphologically resemble cyanobacteria and thus complement the adduced cyanobacterial involvement in stromatolite construction. If cyanobacteria had evolved by 3500 million years ago, this would indicate that nearly all prokaryotic phyla had already evolved and that prokaryotes diversified rapidly on the early Earth.

Australia↗
PubMed2003

[Evolution of bacterial resistance to certain antibacterial agents in horses in a veterinary hospital].

Evolution of bacterial resistance to certain antibacterial agents in horses in a veterinary hospital. A total of 255 antibiograms, conducted according to the Kirby-Bauer method from bacterial isolates collected from horses at the Hôpital Vétérinaire d'Enseignement at the Université de Montréal between 1996 and 1998 were compared with the results obtained about 10 years ago with corresponding bacterial species. A significant increase in the percentage of strains resistant to trimethoprim-sulfamethoxazole (TMP-SXT), penicilline, tetracycline, and to gentamicin was observed. The percentages of isolates of Actinobacillus spp. and coagulase-positive staphylococci resistant to TMP-SXT increased from 0% to 17% and from 0% to 33%, respectively, (P < 0.05). The percentage of isolates of Actinobacillus spp resistant to penicilline also increased from 33% to 73% (P < 0.05). Regular monitoring of the evolution of bacterial resistance to antibacterial agents is indispensable in a hospital structure. The adoption of "good antibiotherapy practices" is essential to guarantee a decrease in the risks of selection and dissemination of a resistant bacterial strain.

Animals↗
PubMedDate not supplied

[Effect of secondary contamination in the dairy industry].

The evolution that has characterized the cheesemaking technique, which has continued to based on automation, has produced an alteration in the causes of contamination of dairy products. It is essential to locate the points of possible pollution and monitor them with appropriate modalities for a good quality of finished products. The purpose of this study was to determine quantitatively and qualitatively the secondary contamination in the production environments of 10 Dairy Industries. Particularly, air, pasteurized milk, curd, surfaces of manufacturing area and water were selected for microbiological tests. Moreover, fresh and ripened cheeses have been checked for microbial contamination. The results of our survey show a large contamination of production environments by Enterobacteriaceae and yeasts, that often cause alterations of dairy products. From the experimental results obtained, some conclusions may be drawn: the microbiological situation of the production environment is precisely reflected on the qualities of processed products. The persistence of an high microbic number/gr. of product and the frequent isolation of pathogenic Staphylococci make doubtful the healthiness of these very common foods. Finally, the A.A. point out the water pollution of the most of dairy industries. It show that disinfections plants are not run correctly.

Air Microbiology↗
PubMedDate not supplied

C-type lectins and galectins mediate innate and adaptive immune functions: their roles in the complement activation pathway.

In recent years, a 'new' pathway for complement activation mediated by the mannose-binding lectin (MBL) has been described as a key mechanism for the mammalian acute phase response to infection. This complement activation pathway is initiated by a non-self recognition step: the binding of a humoral C-type lectin [mannose-binding lectin (MBL)] to microbial surfaces bearing 'foreign' carbohydrate determinants. The recognition factor, MBL, is associated with a serine protease [MBL-associated serine protease (MASP)] which, upon MBL binding to the microbial ligand, activates the complement component C3, leading to either (a) phagocytosis of the opsonized target via the complement receptor, or (b) humoral cell killing via assembly of the membrane attack complex. Galectins (formerly known as S-type lectins) modulate activity of the complement receptor 3 (CR3), the macrophage membrane receptor for complement components C3b and iC3b, downstream products of the MBL pathway which are covalently bound to 'target cells. Galectins also mediate macrophage- and dendrocyte-adhesion to lymphocytes activated by signaling through another C-type lectin, the L-selectin, leading to immunoglobulin-mediated responses. Thus, the functional interplay of MBL, galectins and L-selectin in the acute phase response neutralizes the microbial challenge, and lead to further adaptive immunity. Although the observation of various components of the lectin pathway in different invertebrate species demonstrates the high conservation and ancient roots of the components of innate immunity, there has previously been no evidence supporting the possibility that the integral lectin-mediated complement activation pathway is present in invertebrates. We now have evidence for the coexistence of homologs of all the pathway's key components (MBL, MASP, C3, and galectin) in the protochordate Clavelina picta, suggesting the lectin-mediated pathway of complement activation preceded the immunoglobulin pathway in evolution. Therefore, despite being 'new' to the textbooks, experimental evidence indicates that this pathway is ancient, and has been conserved intact throughout its evolution.

Amino Acid Sequence↗
PubMed2003

Evolution of sfbI encoding streptococcal fibronectin-binding protein I: horizontal genetic transfer and gene mosaic structure.

Streptococcal fibronectin-binding protein is an important virulence factor involved in colonization and invasion of epithelial cells and tissues by Streptococcus pyogenes. In order to investigate the mechanisms involved in the evolution of sfbI, the sfbI genes from 54 strains were sequenced. Thirty-four distinct alleles were identified. Three principal mechanisms appear to have been involved in the evolution of sfbI. The amino-terminal aromatic amino acid-rich domain is the most variable region and is apparently generated by intergenic recombination of horizontally acquired DNA cassettes, resulting in a genetic mosaic in this region. Two distinct and divergent sequence types that shared only 61 to 70% identity were identified in the central proline-rich region, while variation at the 3' end of the gene is due to deletion or duplication of defined repeat units. Potential antigenic and functional variabilities in SfbI imply significant selective pressure in vivo with direct implications for the microbial pathogenesis of S. pyogenes.

Adhesins, Bacterial↗
PubMed2000

Chemical signaling processes in the marine environment.

Understanding the mechanisms by which environmental chemical signals, chemical defenses, and other chemical agents mediate various life-history processes can lead to important insights about the forces driving the ecology and evolution of marine systems. For chemical signals released into the environment, establishing the principles that mediate chemical production and transport is critical for interpreting biological responses to these stimuli within appropriate natural, historical contexts. Recent technological advancements provide outstanding opportunities for new discoveries, thus allowing quantification of interactions between hydrodynamic, chemical, and biological factors at numerous spatial and temporal scales. Past work on chemically mediated processes involving organisms and their environment have emphasized habitat colonization by larvae and trophic relationships. Future research priorities should include these topics as well as courtship and mating, fertilization, competition, symbiosis, and microbial chemical ecology. There are now vast new opportunities for determining how organisms respond to chemical signals and employ chemical defenses under environmentally realistic conditions. Integrating these findings within a larger ecological and evolutionary framework should lead to improved understanding of natural physicochemical phenomena that constrain biological responses at the individual, population, and community levels of organization.

Animals↗
PubMed1999

An attempt to pinpoint the phylogenetic introduction of glutaminyl-tRNA synthetase among bacteria.

Until recently it was believed that most Bacteria form Gln-tRNA(GLN) by the amidation of Glu-tRNA(GLN), only a few members of the gamma subdivision of Proteobacteria being able to charge tRNA(GLN) directly. We undertook a phylogenetic study in an attempt to determine at what point the changeover to the direct system may have occurred. To this end, we selected a number of representative Proteobacteria to see if we could find a division point. We constructed degenerate primers and conducted PCR analysis to identify which Bacteria had Gln-tRNA synthetase, on the one hand, and which had the amidotransferase system, on the other. At the same time, we surveyed data banks of completely sequenced microbial genomes, as well as those for genomes in the process of being sequenced. These combined efforts revealed four Proteobacteria in a phylogenetically intermediate position which have the genetic potential for both mechanisms. Perplexingly, however, three distantly related bacteria were also found to have both enzymes.

Amino Acid Sequence↗
PubMed1990

Model of carbon fixation in microbial mats from 3,500 Myr ago to the present.

Biological carbon fixation is an important part of global carbon cycling and ecology. Fixation that took place 3,500 million years ago is recorded in the laminated sedimentary rock structures known as stromatolites, which are fossilized remains of microbial mat communities. Stromatolites are the most abundant type of fossil found in the Proterozoic (2,500 to 590 Myr ago), but they then declined, possibly because of predation and competition. Using modern microbial mats as analogues for ancient stromatolites, we show that the rate of carbon fixation is higher at the greater levels of atmospheric CO2 that were probably present in the past. We suggest that carbon fixation in microbial mats was not carbon-limited during the early Precambrian, but became carbon-limited as the supply of inorganic carbon decreased. Carbon limitation led to a lower rate of carbon fixation, especially towards the end of the Precambrian. Thus, another reason for the decline of the stromatolites could have been a decrease in available CO2.

Atmosphere↗

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