A microbial sulfolipid. I. Isolation and physiological studies.
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Chemical Phenomena↗
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Physiological and chemical investigations into microbial degradation of synthetic Poly(cis-1,4-isoprene).
Streptomyces coelicolor 1A and Pseudomonas citronellolis were able to degrade synthetic high-molecular-weight poly(cis-1,4-isoprene) and vulcanized natural rubber. Growth on the polymers was poor but significantly greater than that of the nondegrading strain Streptomyces lividans 1326 (control). Measurement of the molecular weight distribution of the polymer before and after degradation showed a time-dependent increase in low-molecular-weight polymer molecules for S. coelicolor 1A and P. citronellolis, whereas the molecular weight distribution for the control (S. lividans 1326) remained almost constant. Three degradation products were isolated from the culture fluid of S. coelicolor 1A grown on vulcanized rubber and were identified as (6Z)-2,6-dimethyl-10-oxo-undec-6-enoic acid, (5Z)-6-methyl-undec-5-ene-2,9-dione, and (5Z,9Z)-6, 10-dimethyl-pentadec-5,9-diene-2,13-dione. An oxidative pathway from poly(cis-1,4-isoprene) to methyl-branched diketones is proposed. It includes (i) oxidation of an aldehyde intermediate to a carboxylic acid, (ii) one cycle of beta-oxidation, (iii) oxidation of the conjugated double bond resulting in a beta-keto acid, and (iv) decarboxylation.
Biodegradation, Environmental↗
Characterization of an autotrophic nitrogen-removing biofilm from a highly loaded lab-scale rotating biological contactor.
In this study, a lab-scale rotating biological contactor (RBC) treating a synthetic NH(4)(+) wastewater devoid of organic carbon and showing high N losses was examined for several important physiological and microbial characteristics. The RBC biofilm removed 89% +/- 5% of the influent N at the highest surface load of approximately 8.3 g of N m(-2) day(-1), with N(2) as the main end product. In batch tests, the RBC biomass showed good aerobic and anoxic ammonium oxidation (147.8 +/- 7.6 and 76.5 +/- 6.4 mg of NH(4)(+)-N g of volatile suspended solids [VSS](-1) day(-1), respectively) and almost no nitrite oxidation (< 1 mg of N g of VSS(-1) day(-1)). The diversity of aerobic ammonia-oxidizing bacteria (AAOB) and planctomycetes in the biofilm was characterized by cloning and sequencing of PCR-amplified partial 16S rRNA genes. Phylogenetic analysis of the clones revealed that the AAOB community was fairly homogeneous and was dominated by Nitrosomonas-like species. Close relatives of the known anaerobic ammonia-oxidizing bacterium (AnAOB) Kuenenia stuttgartiensis dominated the planctomycete community and were most probably responsible for anoxic ammonium oxidation in the RBC. Use of a less specific planctomycete primer set, not amplifying the AnAOB, showed a high diversity among other planctomycetes, with representatives of all known groups present in the biofilm. The spatial organization of the biofilm was characterized using fluorescence in situ hybridization (FISH) with confocal scanning laser microscopy (CSLM). The latter showed that AAOB occurred side by side with putative AnAOB (cells hybridizing with probe PLA46 and AMX820/KST1275) throughout the biofilm, while other planctomycetes hybridizing with probe PLA886 (not detecting the known AnAOB) were present as very conspicuous spherical structures. This study reveals that long-term operation of a lab-scale RBC on a synthetic NH(4)(+) wastewater devoid of organic carbon yields a stable biofilm in which two bacterial groups, thought to be jointly responsible for the high autotrophic N removal, occur side by side throughout the biofilm.
Anaerobiosis↗
Marine microorganisms associated with the food of young salmon.
The biomass of microorganisms in the digestive tracts of young salmon in the sea of Saanich Inlet was examined by (i) the direct microscopic method, (ii) the plate count method and (iii) the physiological method (microbial biomass assumed from the release of carbon dioxide). By all methods, most microbial biomass in foods was shown to decrease during its stay in the digestive organ. This observation was supported by the detection of many bacteria at different stages of digestion. The microbial biomass was quantitatively influenced by the composition of food ingested and by the sampling time.
Journal Article↗
Beyond survival: microbial dispersion via aerosolization as an evolutionary trait.
Airborne dispersion of microorganisms is a constant ecologically significant global process. However, the initial stage of this process, the uplift of microbes to the atmosphere, remains poorly understood as an ecological filter. Differential aerosolization could serve as a potent selector allowing a subset of microorganisms to disperse via air more efficiently, providing potential advantages in establishment in new environments. While traits associated with atmospheric survival and deposition are well documented, microbial aerosolization is still generally presumed to be stochastic, primarily due to the small size of microorganisms and their lack of active biological ejection mechanisms like those found in seeds and larger fungal spores. However, emerging evidence suggests that uplift into the atmosphere is a dynamic interaction between physical forces in the environment and specific biological traits. This review synthesizes observations from genomic source tracking studies and laboratory experiments that describe how preferential enrichment of certain taxa into the atmosphere is based on intrinsic properties including extracellular polymeric substance (EPS) mediated aggregation, cell surface hydrophobicity, surfactant production, and other potentially relevant microbial traits. Additional candidate traits that may contribute to enhanced aerosolization are identified along with the potential mechanistic basis by which they might influence uplift. Future work with controlled chamber studies on single organisms and integration of atmospheric flux measurements with trait-based microbial uplift can provide a mechanistic basis for more accurate models of bioaerosol flux. Improving our comprehension of bioaerosol aerosolization behavior and flux is critical to understanding the dispersal of microorganisms across diverse habitats and their subsequent impacts on ecosystems, global climate, and the spread of diseases.
atmospheric microbiology↗
The physiology and collective recalcitrance of microbial biofilm communities.
Microbial biofilms impinge upon all aspects of our lives. Whilst much of this impact is positive, there are many areas in which the presence and activities of biofilms are regarded as problematic and in need of control. It is in this respect that biofilms reveal their recalcitrance towards many of the long-established antibiotics, and industrial and medical treatment strategies. The nature of the resistance of biofilms, in spite of much research, remains an enigma. Whilst it is recognized that reaction--diffusion limitation properties of the biofilm matrix towards the majority of treatment agents will impede access, this cannot be the sole explanation of the observed resistance. Rather, it will delay the death of cells within the community to various extents. Similarly, it is recognized that biofilm communities are phenotypically heterogeneous and that their eradication will reflect the susceptibility of the most resistant phenotype. The nutrient and gaseous gradients that generate this heterogeneity will, however, be destroyed as a result of antimicrobial treatments and cause the phenotype of the survivors to alter from slow-growing resistant cells to fast-growing susceptible ones. Accordingly both explanations can only delay death of the community. In order to explain more fully the long-term recalcitrance of biofilms towards such a wide variety of biocidal agents, more radical hypotheses must be considered. Amongst these are that multidrug efflux pumps could be up-regulated on expression of a biofilm phenotype. Whilst this is an appealing and simple explanation, because of its ability to explain the breadth of agents to which biofilms are resistant, recent work has suggested that this is not the case. Alternative hypotheses attempt to explain the diversity of agents by invoking a common cause of death for which singular resistance mechanisms could be applied. It is therefore suggested that an altruistic majority of sublethally damaged cells in a population commit suicide (apoptosis), thereby providing some protection to the survivors. A proportion of cells (persisters) is suggested to be defective, or repressed, in their suicide response, and survive. The persisters thereby benefit from the self-sacrifice of their compatriots and maintain the gene pool. A second explanation of the presence of persisters is that the general stress response, well known to include the adoption of a viable, nonculturable state of quiescence, is up-regulated in small pockets of the biofilm community, where nutrients are particularly scarce. Such quiescent cells noted for their resistance towards the metabolically acting biocides would potentially have their dormancy broken after treatment by the replenished supply of nutrients caused by the death of the majority. A more recent hypothesis suggests that extracellular signals, 'alarmones', released from killed cells might prime recipients into a state of resistance. Thus, in biofilm communities deep lying cells might be alerted into a resistant state by the premature death of peripheral cells. It is equally possible that 'alarmones', in this context, are merely the post-treatment 'wake-up' call to a previously quiescent subset of cells. In this review, we attempt to provide a holistic view of the potential mechanisms by which biofilms express resistance. Since these mechanisms are multifaceted then their impact upon resistance will be considered against the context of biofilm formation, growth and maturation.
Bacteria↗
[Some results and prospects of studies in the area of marine biochemistry and biotechnology].
Recent studies on bioactive metabolites from marine macro- and microorganisms are reviewed with 83 refs. Structures of new sulphated and glycosylated secondary metabolites, which have been reported to have antifungal, immunomodulatory, and cytotoxic properties, are given. Some peculiarities of biosynthesis of natural compounds in marine organisms are revealed. It was shown that some natural products, isolated earlier from sponges, are produced by microbial symbionts. Different physiological activities associated with 8000 marine microbial (mainly symbiotic) strains are discussed as well as some prospects of marine biochemistry and biotechnology development.
Animals↗
The use of germfree vertebrates in the study of "physiological" effects of the normal microbial flora. (An aid to elucidate the possible role of intestinal toxic products on ageing).
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Aging↗
Microbial community changes in a perturbed agricultural soil investigated by molecular and physiological approaches.
Changes in soil microbial activity and diversity after incubation either with nitrogen or with a mixture of methane and air were examined. The perturbation by methane and air were characterized in detail and led to reduced diversity and enrichment of methanotrophs which were identified by denaturing gradient gel electrophoresis and 16S rRNA sequencing.
Bacteria↗
Physiologic variation of sucrase activity and microbial counts in human saliva.
Quantitation of salivary sucrase activity has been proposed as a method for the estimation of the level of sucrose consumption. The purpose of the present study was to investigate the physiologic variability of the sucrase activity and microbial counts in paraffin-wax-stimulated saliva of subjects with sound sucrose consumption habits. Variation was analyzed by repeated sampling studies. Intraday variability was investigated by serial analyses of 16 individuals who gave eight samples at 2-h intervals on a single day. Interday variation was studied by analyzing the morning value of 24 individuals on three consecutive days. Interday variability of salivary mutans streptococci, lactobacilli, and yeasts was tested using semiquantitative commercial test kits. The diurnal variation of sucrase activity revealed that the activity in the morning was significantly higher than at noon or at later sampling times of the day. Interday variation was considerable in subjects with high sucrase values. The day-to-day variability of the salivary microbes was considerable for lactobacilli and relatively small for yeasts. A weak positive correlation ranging from 0.732 to 0.741 was found between high sucrase activity values and salivary lactobacilli. Salivary samples should be collected in the morning to differentiate between subjects with high and low sucrase activities.
Adult↗
Microbial partnerships and molecular mechanisms in plant stress physiology for climate-resilient and sustainable farming.
Plant-microbial partnerships and their underlying molecular mechanisms are indispensable, natural drivers of improved nutrient acquisition and stress tolerance in the face of climate-driven environmental challenges. Modern multi-omics tools, when coupled with artificial intelligence and synthetic biology, enable the precise design of targeted bioinoculants and synthetic microbial consortia. Translating these advanced microbiome-based strategies into scalable, field-level agricultural applications provides a sustainable path toward securing global food production while maintaining soil health. Global climate change imposes multifaceted abiotic and biotic stresses on crops, disrupting physiological and molecular processes and threatening agricultural productivity. Plant-associated microbes represent an underexplored yet powerful ally in enhancing crop resilience. This review presents current knowledge of plant-microbe interactions and the molecular mechanisms governing plant stress physiology, with an emphasis on climate-resilient and sustainable farming. Hence, ever-changing environmental cues pose a significant burden on agricultural productivity, and plant-associated microbial communities modulate a cascade of physiological and molecular responses, including production of phytohormones, signaling, regulation of reactive oxygen species homeostasis, and activation of plant immune responses to help plants withstand stress and enhance productivity. Moreover, root exudates, phytohormones, and quorum sensing mediate the central communication networks, facilitating plant-microbe cross talk. Additionally, the advances in OMICs approaches aid in disentangling the molecular underpinnings of these interactions by providing mechanistic insights and potential candidate gene targets for crop improvement and stress resilience. In the post-genomic era, integrating artificial intelligence and big data analysis to optimize microbiome-based strategies for sustainable agriculture is a new frontier for disentangling plant-microbe symbiosis to improve soil health, enhance crop yields, and improve stress tolerance. Thus, by integrating the ecological, physiological, and molecular perspectives, this review highlights the transformative potential of harnessing plant-microbe symbiosis for climate-resilient and sustainable agriculture.
Stress, Physiological↗
Predicting stability of mixed microbial cultures from single species experiments: 2. Physiological model.
In this paper, we study the equilibria of a physiological model describing the continuous culture in which two microbial populations compete for two substitutable resources. This work is an extension of the stability analysis of the phenomenological model of mixed microbial growth [M.M. Ballyk, G.S.K. Wolkowicz, Exploitative competition in the chemostat for two perfectly substitutable resources, Math. Biosci. 118 (1993) 127-180; S.S. Pilyugin, G.T. Reeves, A. Narang, Predicting stability of mixed microbial cultures from single species experiments: 2. Phenomenological model]. Here, we investigate the influence of the peripheral enzymes that catabolize the substrate uptake on the stability of the mixed culture. We show that, under steady state conditions, an increase in the concentration of one substrate inhibits the uptake of the other substrate(s). We present the criteria for existence, uniqueness, and stability of various types of equilibria. We formulate these criteria in terms of growth isoclines and consumption curves for each of the competing species. Since both types of curves can be obtained from a single species experiment, our approach provides a direct connection between theory and experiment and allows one to infer the dynamics of mixed cultures from the dynamics of single species cultures. By expressing the stability criteria in terms of intracellular properties, the model establishes a link between ecology and molecular biology.
Culture Media↗
Physiological and molecular characterization of a microbial community established in unsaturated, petroleum-contaminated soil.
The microbial communities established in soil samples from an unsaturated, petroleum-contaminated zone and from an adjacent uncontaminated site were characterized by physiological and molecular approaches. Possible electron acceptors such as sulfate and nitrate had been completely depleted in these soil samples. Slurries of these soil samples were incubated in bottles in the presence of hydrocarbon indicators (benzene, toluene, xylene and decane), and the degradation of these compounds was examined. Supplementation with electron acceptors stimulated hydrocarbon degradation, although the stimulatory effect was small in the contaminated soil. The initial degradation rates in the contaminated soil under fermentative/methanogenic conditions were comparable to those under aerobic conditions. The microbial populations in the original soil samples were analysed by cloning and sequencing of polymerase chain reaction (PCR)-amplified bacterial and archaeal 16S rRNA gene fragments, showing that the sequences retrieved from these soils were substantially different. For instance, Epsilonproteobacteria, Gammaproteobacteria, Crenarchaeota and Methanosarcinales could only be detected at significant levels in the contaminated soil. Denaturing gradient gel electrophoresis (DGGE) analyses of 16S rRNA gene fragments amplified by PCR from the incubated soil-slurry samples showed that supplementation of the electron acceptors resulted in a shift in the major populations, while the DGGE profiles after incubating the contaminated soil under the fermentative/methanogenic conditions were not substantially changed. These results suggest that petroleum contamination of the unsaturated zone resulted in the establishment of a fermentative/methanogenic community with substantial hydrocarbon-degrading potential.
Bacteria↗
Microbial genome sequencing 2000: new insights into physiology, evolution and expression analysis.
The complete genome sequence has been reported for 24 microbial organisms. The genome organization and gene content of these organisms has revealed an incredible diversity. Nearly half of the open reading frames identified by these sequencing projects are for potential genes with no known biological function. Efforts to make evolutionary sense and biological sense of the gene content of these organisms have been initiated. The greatest future challenge of genomics will be to determine function for the unknown genes.
Bacteria↗
Rhamnose lipids--biosynthesis, microbial production and application potential.
Biosurfactants containing rhamnose and beta-hydroxydecanoic acid and called rhamnolipids are reviewed with respect to microbial producers, their physiological role, biosynthesis and genetics, and especially their microbial overproduction, physicochemical properties and potential applications. With Pseudomonas species, more than 100 g l-1 rhamnolipids were produced from 160 g l-1 soybean oil at a volumetric productivity of 0.4 g l-1 h-1. The individual rhamnolipids are able to lower the surface tension of water from 72 mN m-1 to 25-30 mN m-1 at concentrations of 10-200 mg l-1. After initial testing, rhamnolipids seem to have potential applications in combating marine oil pollution, removing oil from sand and in combating zoosporic phytopathogens. Rhamnolipids are also a source of L-rhamnose, which is already used for the industrial production of high-quality flavor components.
Alkanes↗
[Effects of Cd contamination on paddy soil microbial biomass and enzyme activities and rice physiological indices].
A pot experiment with rice under submerged condition showed that with the increase of Cd concentration, soil microbial biomass carbon (Cmic) and nitrogen (Nmic) increased initially but decreased at a certain concentration, and the turning points varied with different soil types. Soil enzyme activities had the similar variation trend with soil Cmic and Nmic, and the turning points varied with different soil types and soil enzymes. The variation coefficients were in order of dehydrogenase activity > acid phophatase activity > urease activity. Soil respiration rate and metabolic quotient increased tardily with increasing cadmium concentration. The chlorophyll content of rice increased initially but decreased then with the increase of Cd contamination, and the turning points differed with different soil types. Rice proline content and peroxidase activity were enhanced gradually with increasing cadmium concentration. The variation coefficients of rice physiological indices on paddy soils derived from silty loam and clayed red earth were in order of peroxidase activity > chlorophyll content > proline content, and peroxidase activity > proline content > chlorophyll content, respectively. Correlation analysis indicated that there was a close correlation between the variations of soil microbial biomass and enzymatic activities and rice physiological indices under Cd contamination.
Cadmium↗
Determining replication for discrimination among microbial communities in environmental samples using community-level physiological profiles.
A statistical approach was employed to assess microbial community variability within a single 4-l water sample and among 10 independent 4-l water samples from a single location using community-level physiological profiles. Power calculations demonstrated that duplicate analyses could distinguish between two different locations at two times during the year. Variability associated with replicates from a single container or from different containers was nearly the same for the two sites examined. Duplicate assays (one from each of two independent samples) were sufficient to resolve the between-site differences at alpha=0.05 with power exceeding 0.95 at both times of the year. Similar methods are recommended to determine the appropriate number of replicates for environments of interest.
Journal Article↗
Microbial responses to microgravity and other low-shear environments.
Microbial adaptation to environmental stimuli is essential for survival. While several of these stimuli have been studied in detail, recent studies have demonstrated an important role for a novel environmental parameter in which microgravity and the low fluid shear dynamics associated with microgravity globally regulate microbial gene expression, physiology, and pathogenesis. In addition to analyzing fundamental questions about microbial responses to spaceflight, these studies have demonstrated important applications for microbial responses to a ground-based, low-shear stress environment similar to that encountered during spaceflight. Moreover, the low-shear growth environment sensed by microbes during microgravity of spaceflight and during ground-based microgravity analogue culture is relevant to those encountered during their natural life cycles on Earth. While no mechanism has been clearly defined to explain how the mechanical force of fluid shear transmits intracellular signals to microbial cells at the molecular level, the fact that cross talk exists between microbial signal transduction systems holds intriguing possibilities that future studies might reveal common mechanotransduction themes between these systems and those used to sense and respond to low-shear stress and changes in gravitation forces. The study of microbial mechanotransduction may identify common conserved mechanisms used by cells to perceive changes in mechanical and/or physical forces, and it has the potential to provide valuable insight for understanding mechanosensing mechanisms in higher organisms. This review summarizes recent and future research trends aimed at understanding the dynamic effects of changes in the mechanical forces that occur in microgravity and other low-shear environments on a wide variety of important microbial parameters.
Adaptation, Physiological↗