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PubMed2006

Microbial community structure and dynamics in the largest natural French lake (Lake Bourget).

We investigated the dynamics and diversity of heterotrophic bacteria, autotrophic and heterotrophic flagellates, and ciliates from March to July 2002 in the surface waters (0-50 m) of Lake Bourget. The heterotrophic bacteria consisted mainly of "small" cocci, but filaments (>2 microm), commonly considered to be grazing-resistant forms under increased nanoflagellate grazing, were also detected. These elongated cells mainly belonged to the Cytophaga-Flavobacterium (CF) cluster, and were most abundant during spring and early summer, when mixotrophic or heterotrophic flagellates were the main bacterial predators. The CF group strongly dominated fluorescent in situ hybridization-detected cells from March to June, whereas clear changes were observed in early summer when Beta-proteobacteria and Alpha-proteobacteria increased concomitantly with maximal protist grazing pressures. The analysis of protist community structure revealed that the flagellates consisted mainly of cryptomonad forms. The dynamics of Cryptomonas sp. and Dinobryon sp. suggested the potential importance of mixotrophs as consumers of bacteria. This point was verified by an experimental approach based on fluorescent microbeads to assess the potential grazing impact of all protist taxa in the epilimnion. From the results, three distinct periods in the functioning of the epilimnetic microbial loop were identified. In early spring, mixotrophic and heterotrophic flagellates constituted the main bacterivores, and were regulated by the availability of their resources mainly during April (phase 1). Once the "clear water phase" was established, the predation pressure of metazooplankton represented a strong top-down force on all microbial compartments. During this period only mixotrophic flagellates occasionally exerted a significant bacterivory pressure (phase 2). Finally, the early summer was characterized by the highest protozoan grazing impact and by a rapid shift in the carbon pathway transfer, with a fast change-over of the main predators contribution, i.e., mixotrophic, heterotrophic flagellates and ciliates in bacterial mortality. The high abundance of ciliates during this period was consistent with the high densities of resources (heterotrophic nanoflagellates, algae, bacteria) in deep layers containing the most chlorophyll. Bacteria, as ciliates, responded clearly to increasing phytoplankton abundance, and although bacterial grazing impact could vary largely, bacterial abundance seemed to be primarily bottom-up regulated (phase 3).

Animals↗
PubMed2006

Compaction of forest soil by logging machinery favours occurrence of prokaryotes.

Soil compaction caused by passage of logging machinery reduces the soil air capacity. Changed abiotic factors might induce a change in the soil microbial community and favour organisms capable of tolerating anoxic conditions. The goals of this study were to resolve differences between soil microbial communities obtained from wheel-tracks (i.e. compacted) and their adjacent undisturbed sites, and to evaluate differences in potential anaerobic microbial activities of these contrasting soils. Soil samples obtained from compacted soil had a greater bulk density and a higher pH than uncompacted soil. Analyses of phospholipid fatty acids demonstrated that the eukaryotic/prokaryotic ratio in compacted soils was lower than that of uncompacted soils, suggesting that fungi were not favoured by the in situ conditions produced by compaction. Indeed, most-probable-number (MPN) estimates of nitrous oxide-producing denitrifiers, acetate- and lactate-utilizing iron and sulfate reducers, and methanogens were higher in compacted than in uncompacted soils obtained from one site that had large differences in bulk density. Compacted soils from this site yielded higher iron-reducing, sulfate-reducing and methanogenic potentials than did uncompacted soils. MPN estimates of H2-utilizing acetogens in compacted and uncompacted soils were similar. These results indicate that compaction of forest soil alters the structure and function of the soil microbial community and favours occurrence of prokaryotes.

Fatty Acids↗
PubMed2026

Elevation-structured viral ecological strategies along glacier-fed rivers on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau, a climate-vulnerable source of Asia's major rivers, harbors underexplored viral communities critical to ecosystem functions. By integrating 597 metagenomes from the Yangtze, Yellow, Lancang, and Yarlung Tsangpo rivers with 85 public available glacial metagenomes (Tibetan Glacier Genome and Gene catalog), we built the Glacier-to-River Virome Catalogue, encompassing 36,358 vOTUs and 897,250 viral protein clusters, to decode viral adaptation and ecological influence across elevation gradients. Our results reveal that high-altitude conditions favor viruses with elevated Guanine-Cytosine content, larger genomes and more cold-adaptation genes. A central finding is a systematic viral lifestyle shift from temperate in glaciated regions to lytic viruses downstream, accompanied with decline of pathogens carrying antibiotic resistance genes along the glacier-to-river gradients. Further, viral auxiliary metabolic genes transition from glacier nutrient scavenging (e.g., nitrogen and sulfur transporters) to downstream mineralization processes (e.g., denitrification) in plains highlights their role in biogeochemical cycling. These findings position viruses as pivotal regulators of microbial community structural and functional dynamics to glacier-to-river gradient change and biogeochemistry in the Qinghai-Tibet Plateau, providing critical insights into climate response in vulnerable Asian water towers.

Ice Cover↗
PubMed2004

Light-induced intramolecular charge movements in microbial rhodopsins in intact E. coli cells.

Microbial rhodopsins undergo cyclic photochemical reactions (photocycles) in which proton transfers and conformational changes result in charge displacements during transitions between photocycle intermediates. We report a new photoelectric method to monitor charge movements during rhodopsin photocycling with fast kinetic resolution in suspensions of intact E. coli cells. The method monitors electrical currents resulting from asymmetric photoexcitation of microbial rhodopsins by a unilateral laser flash, and kinetically resolves intramolecular charge movements. We investigated E. coli-expressed proton-transporting rhodopsins, specifically green- and blue-absorbing proteorhodopsins (GPR and BPR, respectively) from uncultivated marine plankton, and sensory rhodopsins, namely receptors from Natronomonas pharaonis and Anabaena (Nostoc) sp. PCC7120. Kinetic components of the currents correlate with photochemical transformations of the pigments, and the integrated current measures net transport by the proton-pumping rhodopsins. The photoelectric measurements distinguish between known light-driven transporters and photosensors, and reveal differences in proton transfer reactions in the two tested proton pumps. Screening of nine newly identified proteorhodopsins reveals two with GPR-type charge movements, five with BPR-type, and two with the characteristics of the sensory rhodopsins. The approach developed in the present work provides a direct, rapid and informative method for studying electrogenic events in rhodopsin photocycles and also gives a clue to functions of newly found microbial rhodopsins in nature.

Anabaena↗
PubMed2026

Genome-resolved analysis of colonization factor repertoires reveals ecological stratification in cervid gut microbiomes.

INTRODUCTION: Colonization factors (CFs) are important microbial traits associated with persistence and host adaptation in the gut, yet their large-scale organization in cervid gut microbiomes remains unclear. METHODS: A total of 3,311 non-redundant high-quality metagenome-assembled genomes (MAGs), derived from 688 cervid gut metagenomic samples across 15 publicly available projects and one in-house dataset, were analyzed. CF-associated genes were identified by comparison against the GHA CF database, and CF repertoires were characterized at genome, host-species, and gastrointestinal-segment levels. RESULTS: A total of 138,729 CF-associated genes spanning 71 CF families were identified. MAGs from Cervinae contained richer CF repertoires than those from Caprinae, and CF47 (Peptidase_C69), CF24_29 (QueH), and CF18 (Glycos_transf_2) were among the most prevalent families. CF repertoires were strongly structured by taxonomy, showed a moderate association with bacterial phylogenetic distance, and formed two recurrent genome-level configurations with distinct KEGG functional profiles. Integration of sample metadata further revealed differentiation of CF repertoires across host species and gastrointestinal segments, representing the major ecological dimensions examined in this study. Segment-associated CF variation was accompanied by redistribution of broader functional profiles, including enrichment of carbohydrate and lipid metabolism in the jejunum, membrane transport in the ileum, xenobiotics biodegradation in the cecum, and environmental adaptation in the rumen. DISCUSSION: These findings provide a genome-resolved view of CF repertoire organization in cervid gut microbiomes and demonstrate that colonization-associated functions are structured across microbial lineages and ecological contexts. This study highlights the importance of considering microbial taxonomy and host-associated environments when interpreting the distribution of CF repertoires in mammalian gut ecosystems.

Cervidae↗
PubMed2004

The third signal in T cell-mediated autoimmune disease?

The initial event in the pathogenesis of autoimmune disease is thought to be the priming of naive autoreactive T cells by an infection with a cross-reactive microorganism. Although such cross-reactive priming should be a common event, autoimmune disease does not frequently develop. This situation is reflected after the immunization of C57BL/6 mice with the neuroantigen myelin oligodendrocyte glycoprotein (MOG) with CFA, which primes a type 1 T cell response but does not lead to clinical or histological manifestation of experimental allergic encephalomyelitis unless pertussis toxin is injected in addition. We show in this study that, in MOG:CFA-primed mice, the autoimmune CNS pathology develops after intracerebral deposition of TLR9-activating CpG oligonucleotides, but not following non-CpG oligonucleotide injection or after aseptic cryoinjury of the brain. Thus, access of primed MOG-specific Th1 cells to the uninflamed CNS or to CNS undergoing sterile inflammation did not suffice to elicit autoimmune pathology; only if the APC in the target organ were activated in addition by the TLR9-stimulating microbial product did they exert local effector functions. The data suggest that such licensing of APC in the target organ by microbial stimuli represents a checkpoint for functional self-tolerance. Therefore, microorganisms unrelated to the cross-reactive agent that primes the autoreactive T cells could dictate the onset and exacerbation of autoimmune diseases.

Animals↗
PubMed2004

Review of the knowledge of microbial contamination of the Russian manned spacecraft.

The 15-year experience of orbital station Mir service demonstrated that specifically modified space vehicle environments allows for the consideration of spaceship habitats as a certain ecological niche of microbial community development and functioning, which was formed from the organisms of different physiological and taxonomical groups. The base unit of the orbital station (OS) Mir was launched on February 20, 1986, and on March 13 the first crew arrived to it. From that moment a unique microbiocenosis started forming in the closed environment of the space station, and vital activity of the microorganisms continued for the next 15 years in a specifically changed environment, in conditions of continuous influence of a set of factors intrinsic to space flight. A total of 234 species of bacteria and fungi were found onboard orbital station Mir, among which microorganisms capable of resident colonization of the environment of space objects as a unique anthropotechnological niche were revealed. In such conditions the evolution of microflora is followed by the rise of medical and technical risks that can affect both sanitary-microbiological conditions of the environment and the safety and reliability characteristics of space equipment. The latter is caused by progressing biological damage to the structural materials. The microbial loading dynamic does not have linearly progressing character, but it is a wavy process of alternation of the microflora activation and stabilization phases; on this background there is a change of the dominating species by quantity and prevalence. The accumulated data is evidence of the necessity of the constant control of the microbial environmental factors to maintain their sanitary and microbiological optimum condition and to prevent the processes of constructional materials biodestruction.

Air Microbiology↗
PubMed2006

2,4-D impact on bacterial communities, and the activity and genetic potential of 2,4-D degrading communities in soil.

The key role of telluric microorganisms in pesticide degradation is well recognized but the possible relationships between the biodiversity of soil microbial communities and their functions still remain poorly documented. If microorganisms influence the fate of pesticides, pesticide application may reciprocally affect soil microorganisms. The objective of our work was to estimate the impact of 2,4-D application on the genetic structure of bacterial communities and the 2,4-D-degrading genetic potential in relation to 2,4-D mineralization. Experiments combined isotope measurements with molecular analyses. The impact of 2,4-D on soil bacterial populations was followed with ribosomal intergenic spacer analysis. The 2,4-D degrading genetic potential was estimated by real-time PCR targeted on tfdA sequences coding an enzyme specifically involved in 2,4-D mineralization. The genetic structure of bacterial communities was significantly modified in response to 2,4-D application, but only during the intense phase of 2,4-D biodegradation. This effect disappeared 7 days after the treatment. The 2,4-D degrading genetic potential increased rapidly following 2,4-D application. There was a concomitant increase between the tfdA copy number and the 14C microbial biomass. The maximum of tfdA sequences corresponded to the maximum rate of 2,4-D mineralization. In this soil, 2,4-D degrading microbial communities seem preferentially to use the tfd pathway to degrade 2,4-D.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2003

Antibody-enhanced pneumococcal adherence requires IgA1 protease.

IgA, the major class of Ig in secretions, classically functions by interfering with microbial attachment to host tissues. Many mucosal pathogens, including Streptococcus pneumoniae, express an IgA1 protease that may circumvent the protective effects of this Ig subclass. Because these proteases are specific for human IgA1, we generated human mAbs to the major surface antigen of the pneumococcus, its capsular polysaccharide, and tested their effect in a colonization model of bacterial adherence to respiratory epithelial cells in culture. Rather than inhibiting adherence, type-specific IgA1 markedly enhanced bacterial attachment to host cells, but only when cleaved by IgA1 protease. Neither antibodies of protease-insensitive subclasses (IgA2 and IgG) nor those directed against heterologous capsules had such activity. The adherence-promoting properties of cleaved antibodies correlated with the cationic characteristics of their variable segments, suggesting that bound Fab fragments may neutralize the inhibitory effect of negatively charged capsules on adhesive interaction with host cells. Coating of pneumococci with anticapsular polysaccharide antibody unmasked the bacterial phosphorylcholine ligand, allowing for increased adherence mediated by binding to the platelet activating factor receptor on epithelial cells. In addition, our findings provide evidence for a novel function of bacterial IgA1 proteases. These enzymes may enable pathogens to subvert the antigen specificity of the humoral immune response to facilitate adhesive interactions and persistence on the mucosal surface.

Adult↗
PubMed2026

Comparative profiling of microbial community structure, enzyme potential, metabolic features, and volatile composition in craft and Jiafan Huangjiu processes.

Craft Huangjiu and Jiafan Huangjiu represent two distinct industrial Huangjiu product outcomes with contrasting volatile profiles. This study compared craft Huangjiu (L70) and Jiafan Huangjiu (L79) to characterize their physicochemical, microbial, gene-level functional, metabolic, and volatile features. Because L70 involved mid-fermentation addition of finished Huangjiu, this comparison was not intended to isolate the sole effect of fermentation interruption versus continued fermentation. L79 showed more extensive carbon and nitrogen utilization, with lower residual substrates and higher ethanol and acetic acid contents than L70, whereas L70 retained a less complete fermentation state. At the volatile level, GC-MS and volatile metabolomics consistently showed an ester-enriched profile in L79 and a more alcohol-dominant profile in L70. FlavorDB-based putative annotation and threshold-based OAV analysis further indicated distinct database-assigned descriptor distributions and potential odor-active compounds, with more OAV > 1 ester-related compounds in L79. Metagenomic analysis showed that L70 was dominated by Lactobacillus acetotolerans, whereas L79 contained higher relative abundances of Saccharomyces cerevisiae, Aspergillus oryzae, Aspergillus flavus, and Fructilactobacillus fructivorans. Metagenomic functional annotation showed higher representation of hydrolysis-related CAZy genes and ester-related enzyme annotations in L79. KEGG-based pathway mapping further indicated greater gene-level potential for ethanol-, acetate-, and acetyl-CoA-related metabolism in L79. Accordingly, the L70 profile should be interpreted as the integrated final-product outcome of process intervention, exogenous input, and subsequent fermentation. The findings provide a comparative basis for future flavor regulation and process optimization in Huangjiu and other fermented alcoholic beverages.

Volatile Organic Compounds↗
PubMed2004

Functional domains of HSP70 stimulate generation of cytokines and chemokines, maturation of dendritic cells and adjuvanticity.

Microbial HSP70 (heat-shock protein 70) consists of three functionally distinct domains: an N-terminal 44 kDa ATPase portion (amino acids 1-358), followed by an 18 kDa peptide-binding domain (amino acids 359-494) and a C-terminal 10 kDa fragment (amino acids 495-609). Immunological functions of these three different domains in stimulating monocytes and dendritic cells have not been fully defined. However, the C-terminal portion (amino acids 359-610) stimulates the production of CC chemokines, IL-12 (interleukin-12), TNFalpha(tumour necrosis factor alpha), NO and maturation of dendritic cells and also functions as an adjuvant in the induction of immune responses. In contrast, the ATPase domain of microbial HSP70 mostly lacks these functions. Since the receptor for HSP70 is CD40, which with its CD40 ligand constitutes a major co-stimulatory pathway in the interaction between antigen-presenting cells and T-cells, HSP70 may function as an alternative ligand to CD40L. HSP70-CD40 interaction has been demonstrated in non-human primates to play a role in HIV infection, in protection against Mycobacterium tuberculosis and in conversion of tolerance to immunity.

Adaptation, Physiological↗
PubMed2001

Molecular phylogenetic profiling of prokaryotic communities in guts of termites with different feeding habits.

Termites are an important group of terrestrial insects that harbor an abundant gut microbiota, many of which contribute to digestion, termite nutrition and gas (CH(4), CO(2) and H(2)) emission. With 2200 described species, termites also provide a good model to study relationships between host diet and gut microbial community structure and function. We examined the relationship between diet and gut prokaryotic community profiles in 24 taxonomically and nutritionally diverse species of termites by using nucleic acid probes targeting 16S-like ribosomal RNAs. The relative abundance of domain-specific 16S-like rRNAs recovered from gut extracts varied considerably (ranges: Archaea (0-3%); Bacteria (15-118%)). Although Bacteria were always detectable and the most abundant, differences in domain-level profiles were correlated with termite diet, as evidenced by higher relative abundances of Archaea in guts of soil-feeding termites, compared to those of wood-feeding species in the same family. The oligonucleotide probes also readily distinguished gut communities of wood-feeding taxa in the family Termitidae (higher termites) from those of other wood-feeding termite families (lower termites). The relative abundances of 16S-like archaeal rRNA in guts were positively correlated with rates of methane emission by live termites, and were consistent with previous work linking high relative rates of methanogenesis with the soil (humus)-feeding habit. Probes for methanogenic Archaea detected members of only two families (Methanobacteriaceae and Methanosarcinaceae) in termite guts, and these typically accounted for 60% of the all archaeal probe signal. In four species of termites, Methanosarcinaceae were dominant, a novel observation for animal gut microbial communities, but no clear relationship was apparent between methanogen family profiles and termite diet or taxonomy.

Journal Article↗
PubMed2001

Elevated iron status increases bacterial invasion and survival and alters cytokine/chemokine mRNA expression in Caco-2 human intestinal cells.

Iron status affects both microbial growth and immune function. Mammalian iron homeostasis is maintained primarily by regulating the absorption of the micronutrient in the proximal small intestine. The iron concentration of the enterocyte can fluctuate widely in response to both dietary and whole body iron status, as well as in response to infections. The possibility that an enterocyte with an elevated iron concentration is more susceptible to invasion by enteric pathogens is not known. Therefore, we examined the impact of enterocyte iron status on the invasion and survival of an enteric pathogen, as well as on the levels of several cytokine and chemokine mRNAs by the host cell. The enterocyte-like Caco-2 human intestinal cell line and Salmonella enteritidis served as the models to examine the effect of iron on the host-parasite interaction. Iron status of Caco-2 cells was altered by incubation in serum-free medium supplemented with varying levels of iron. Elevated iron status of Caco-2 cells increased the efficiency of the invasion and the number of bacteria surviving in the intracellular environment. Caco-2 cells constitutively expressed transforming growth factor-beta1, interleukin-8, monocyte chemotactic protein-1, tumor necrosis factor-alpha and interleukin-1beta, and infection with S. enteritidis increased the relative quantities of all cytokine/chemokine mRNAs except interleukin-1beta. Elevated iron status of Caco-2 cells decreased the levels of cytokine/chemokine mRNAs by 25-45% in uninfected cells. In contrast, bacterial infection was associated with a 21-95% increase in cytokine/chemokine mRNAs levels in Caco-2 cells with higher iron concentration compared with infected cells with lower iron concentration. These data support the hypothesis that elevated enterocyte iron status increases susceptibility to infection and exacerbates the mucosal inflammatory response initiated by microbial invasion by increasing cytokine/chemokine expression.

Analysis of Variance↗
PubMed2003

Pathogen self-defense: mechanisms to counteract microbial antagonism,.

Natural and agricultural ecosystems harbor a wide variety of microorganisms that play an integral role in plant health, crop productivity, and preservation of multiple ecosystem functions. Interactions within and among microbial communities are numerous and range from synergistic and mutualistic to antagonistic and parasitic. Antagonistic and parasitic interactions have been exploited in the area of biological control of plant pathogenic microorganisms. To date, biocontrol is typically viewed from the perspective of how antagonists affect pathogens. This review examines the other face of this interaction: how plant pathogens respond to antagonists and how this can affect the efficacy of biocontrol. Just as microbial antagonists utilize a diverse arsenal of mechanisms to dominate interactions with pathogens, pathogens have surprisingly diverse responses to counteract antagonism. These responses include detoxification, repression of biosynthetic genes involved in biocontrol, active efflux of antibiotics, and antibiotic resistance. Understanding pathogen self-defense mechanisms for coping with antagonist assault provides a novel approach to improving the durability of biologically based disease control strategies and has implications for the deployment of transgenes (microorganisms or plants).

Bacteria↗
PubMed2004

[Effects of forest restoration patterns on soil microbial communities].

In this paper, soil microbial community properties of five vegetation patterns were measured by bacterial, microbial biomass carbon and metabolic diversity (BIOLOG) assays to evaluate the effects of different forest restoration patterns on soil microbial community. The results showed that among five sampling sites, soil microbial biomass carbon and bacterial amount were the highest under natural secondary forest, while those in CK were the least. In BIOLOG assays, the average well colour development (AWCD) and the richness and diversity indices indicated the differences of microbial metabolic diversity. The variation tendency of the indices was the same as that of microbial biomass and bacterial amount. It is suggested that under natural secondary forest, soil microbial community had a stronger ability of utilizing carbon source and a greater functional diversity than that in plantations and CK. The metabolic diversity of microbial communities in 0-20 and 20-40 cm soil layers showed a fairly good correlation with root biomass (r = 0.933, P < 0.05; r = 0.925, P < 0.05). In a word, soil microbial biomass, bacterial amount and metabolic diversity patterns were the highest under natural secondary forest, and natural restoration should be more propitious to improve the structure and function of soil microbial community.

Biodiversity↗
PubMed2003

Enteral feeding of premature infants with Saccharomyces boulardii.

BACKGROUND: Saccharomyces boulardii (SB) is a yeast that acts both as a probiotic and as a polyamine producer. Probiotics prevent the overgrowth of pathogens in the gut while polyamines enhance intestinal maturation. The aim of this randomized study was to investigate the ability of SB to modify the gut microbial ecology and its function. METHODS: A total of 87 healthy babies with gestational age 28-32 weeks were studied. They were randomly assigned to receive a preterm formula to which SB or maltodextrins was added for 30 days. Evaluations were made on the following: SB tolerance and weight gain, faecal flora analysis, intestinal D-xylose absorption and faecal lipid excretion. RESULTS: SB was well tolerated by the infants. There was no difference in weight gain between the two groups. Median log of colony forming units per gram of faeces for Escherichia coli and enterococci was significantly lower in the SB group [E. coli: 2.67 (0.045) vs. 2.75 (0.058), P<0.001; enterococci: 2.14 (0.359) vs. 2.19 (0.138), P<0.05]. On the other hand, the number of bifidobacteria and staphylococci in the stools was significantly higher in the SB group [bifidobacteria: 2.65 (0.083) vs. 2.27 (0.075), P<0.001; staphylococci: 1.23 (0.869) vs. 0.6 (0.281), P<0.001]. D-Xylose and lipid absorption was not improved by SB [median blood D-xylose: 1.5 (0.4) mmol/l vs. 1.35 (0.3) mmol/l, P>0.1; median stool steatocrit: 64% (3.05%) vs. 65% (2.72%) P>0.5]. CONCLUSIONS: An SB-supplemented formula is well tolerated by preterm infants, it has a beneficial effect on stool flora bringing it closer to that of breast fed babies but it does not improve D-xylose or lipid gut absorption.

Colony Count, Microbial↗
PubMed2004

Microscale and molecular assessment of impacts of nickel, nutrients, and oxygen level on structure and function of river biofilm communities.

Studies were carried out to assess the influence of nutrients, dissolved oxygen (DO) concentration, and nickel (Ni) on river biofilm development, structure, function, and community composition. Biofilms were cultivated in rotating annular reactors with river water at a DO concentration of 0.5 or 7.5 mg liter(-1), with or without a combination of carbon, nitrogen, and phosphorus (CNP) and with or without Ni at 0.5 mg liter(-1). The effects of Ni were apparent in the elimination of cyanobacterial populations and reduced photosynthetic biomass in the biofilm. Application of lectin-binding analyses indicated changes in exopolymer abundance and a shift in the glycoconjugate makeup of the biofilms, as well as in the response to all treatments. Application of the fluorescent live-dead staining (BacLight Live-Dead staining kit; Molecular Probes, Eugene, Oreg.) indicated an increase in the ratio of live to dead cells under low-oxygen conditions. Nickel treatments had 50 to 75% fewer 'live' cells than their corresponding controls. Nickel at 0.5 mg liter(-1) corresponding to the industrial release rate concentration for nickel resulted in reductions in carbon utilization spectra relative to control and CNP treatments without nickel. In these cases, the presence of nickel eliminated the positive influence of nutrients on the biofilm. Other culture-dependent analyses (plate counts and most probable number) revealed no significant treatment effect on the biofilm communities. In the presence of CNP and at both DO levels, Ni negatively affected denitrification but had no effect on hexadecane mineralization or sulfate reduction. Analysis of total community DNA indicated abundant eubacterial 16S ribosomal DNA (rDNA), whereas Archaea were not detected. Amplification of the alkB gene indicated a positive effect of CNP and a negative effect of Ni. The nirS gene was not detected in samples treated with Ni at 0.5 mg liter(-1), indicating a negative effect on specific populations of bacteria, such as denitrifiers, resulting in a reduction in diversity. Denaturing gradient gel electrophoresis revealed that CNP had a beneficial impact on biofilm bacterial diversity at high DO concentrations, but none at low DO concentrations, and that the negative effect of Ni on diversity was similar at both DO concentrations. Notably, Ni resulted in the appearance of unique bands in 16S rDNA from Ni, DO, and CNP treatments. Sequencing results confirmed that the bands belonged to bacteria originating from freshwater and marine environments or from agricultural soils and industrial effluents. The observations indicate that significant interactions occur between Ni, oxygen, and nutrients and that Ni at 0.5 mg liter(-1) may have significant impacts on river microbial community diversity and function.

Biofilms↗
PubMed1979

Observations on the biological roles of sulphatases.

Until recently little was known about the biological roles played by sulphatase enzymes, owing in part to the selection of assay substrates that were convenient but only removely related to the natural substrates. Once this was recognized the elucidation of function proceeded more rapidly. Microbial sulphatases appear to have roles to play in the nutrition of individual microorganisms whilst collectively they enable sulphur, returned to soils and waters in the form of sulphate esters, to be made available for recycling. In contrast, with one or two important exceptions, mammalian sulphatases are concerned, in association with other enzymes, with the turnover of macromolecules. Still defying understanding are the roles of sulphatases acting on adenosine 5'-phosphosulphate (APT) and 3'-phosphoadenosine 5'-phosphosulphate (PAPA). APS sulphatases have now been purified from ox-liver lysosomes and cytosol and from a strain of Comamonas terrigena. The lysosomal enzyme shows wide specificity and can hydrolyse ATP, ADP, FED and pyrophosphate. The cytosol enzyme is apparently specific and may be active only when cellular concentrations of ATP are low. The bacterial enzyme is also specific and has properties and a cellular localization that suggest the possibility of its involvement in sulphate transport.

Adenosine Monophosphate↗