Retention of the Gram-negative bacterium SW8 on surfaces under conditions relevant to the subsurface environment: Effects of conditioning films and substratum nature

Abstract Shallow (5–13 m) and deep (35–65 m) groundwaters were evaluated for their ability to generate conditioning films which affect bacterial adhesion to natural (sandstone, shale, andesite) and man-made substrata (polypropylene, stainless steel). Water contact angles indicated that all water samples produced conditioning films. Most films modified retention of the nonmotile Gram-negative bacterium SW8, but attachment of the organism did not correlate with water contact angles. Each borewater produced conditioning films with a characteristic attachment profile of SW8. Films adsorbed from standing borewaters often retained SW8 in different numbers than coatings derived from pumped bores. Groundwater chemistry was very heterogeneous and microbiological data indicated the presence of a diverse aerobic and anaerobic microbial community. These results indicate that conditioning films derived from dissolved compounds may play a significant role in controlling the interaction of bacteria with substrata in the subsurface.     

Effect of bacterial heterogeneity on adhesion to uniform collectors by monoclonal populations

Abstract Transport of bacteria over significant distances through aquifer sediments occurs primarily among bacteria with low affinity for sediment materials. Bacterial affinity for a uniform collector surface has been represented quantitatively by a collision efficiency (α), defined as the fraction of colliding cells that adhere to the collector surface. Using a new method for estimating α during advective transport of monoclonal bacterial populations through a uniform bed of 40-μm borosilicate glass spheres, we found that α decreased 10-fold over a bed depth of only 1 cm. Depth-dependent differences in α were not related to variation in bacterial size or intra-strain genetic variation. Intra-population heterogeneity in biocolloid-collector affinity may be important determinant of subsurface bacterial transport characteristics, with critical implications for pathogen transport and dispersal of bacteria for the remediation of hazardous waste.     

Geochemical Influence on Diversity and Microbial Processes in High Temperature Oil Reservoirs

The diversity of thermophilic microbial assemblages detected within two neighboring high temperature petroleum formations was shown to closely parallel the different geochemical regimes existing in each. A high percentage of archaeal 16S rRNA gene sequences, related to thermophilic aceticlastic and hydrogenotrophic methanogens, were detected in the natural gas producing Rincon Formation. In contrast, rRNA gene libraries from the highly sulfidogenic Monterey Formation contained primarily sulfur-utilizing and fermentative archaea and bacteria. In addition to the variations in microbial community structure, microbial activities measured in microcosm experiments using high temperature production fluids from oil-bearing formations also demonstrated fundamental differences in the terminal respiratory and redox processes. Provided with the same suite of basic energy substrates, production fluids from the South Elwood Rincon Formation actively generated methane, while thermophilic microflora within the Monterey production fluids were dominated by hydrogen sulfide producing microorganisms. In both cases, molecular hydrogen appeared to play a central role in the stimulation of carbon and sulfur cycling in these systems. In methanogenic production fluids, the addition of sulfur compounds induced a rapid shift in the terminal electron accepting process, stimulating hydrogen sulfide formation and illustrating the metabolic versatility of the subsurface thermophilic assemblage. The high similarity between microbial community structure and activity corresponding with the prevalent geochemical conditions observed in deep subsurface petroleum reservoirs suggests that the resident microflora have adapted to the subsurface physicochemical conditions and may actively influence the geochemical environment in situ.     

Subsurface cisterns in the Purkinje cells of cerebellum of Syrian hamster

Summary Three types of subsurface cisterns were observed in Purkinje cells of the cerebellum of the Syrian hamster. The type-1 cisterns are subsynaptic, related to axosomatic synapses, and are separated from the postsynaptic cell membranes with distances of 400–800 Å. These are probably modified rough surfaced endoplasmic reticulum. The type-2 cisterns are closely apposed to the surface membranes of Purkinje cells, and have very little intracisternal space except at the dilated lateral edges. The type-3 cisterns are similar in structure to the type-2 cisterns but in addition are closely associated with mitochondria. The type-2 and type-3 cisterns appear between one and two weeks after birth and are still present in adults, having almost the same frequency of occurrence. Thin cell processes opposite the type-2 and type-3 cisterns are considered to be glial cell processes. The morphological details of these types of subsurface cisterns are described here, and their possible functional significance is briefly discussed.This work was carried out at the Department of Anatomy, University of Minnesota, Minneapolis, USA, and was supported by grants from the China Medical Board of New York and Anatomical Training Grant GM114 from the USPHS.Dr. Takahashi wishes to express his sincere thanks to Dr. A. Lazarow and Dr. R. L. Wood of the Department of Anatomy, University of Minnesota, who enabled him to use facilities for electron microscopy.     

Light as a possible regulator of MIB-producing Planktothrix in source water reservoir,mechanism and in-situ verification

The typical musty/earthy odor-causing compound, 2-methylisoborneol (MIB), is usually associated with the occurrence and proliferation of benthic/subsurface-living cyanobacteria in source water. Control of MIB-producing cyanobacteria in source water may greatly reduce the processing burden for drinking water treatment plants. We explored the mechanism and feasibility of restricting the growth of subsurface-living Planktothrix sp. by reducing underwater light availability. The effects of light intensity (5, 17, 36, 85, and 250 μmol photons m⁻² s⁻¹) on the growth and MIB production of Planktothrix sp. were first determined using batch culture, followed by an in-situ experiment deployed at different depths (0.5, 1.5, 3.5, and 5.0 m) in a drinking source water reservoir (Miyun Reservoir, China) to verify the laboratory results. The optimum conditions for growth (7.5 × 10⁸ cells L⁻¹) and MIB production ((1300 ± 29) μg L⁻¹) of Planktothrix sp. were achieved at 85 μmol photons m⁻² s⁻¹ in the laboratory and at 1.5 m (the corresponding average light intensity of 66 μmol photons m⁻² s⁻¹) in the field. The minimum light requirement for the growth of Planktothrix sp. (4.4 μmol photons m⁻² s⁻¹) was determined according to the laboratory data. While the in-situ experiment further indicated that Planktothrix sp. could not successfully grow at depths of 5 m where light intensity was below the minimum light requirement. In addition, the history data also verified the negative relationships between underwater light availability and MIB concentration.     

3种革兰氏阴性细菌及其L型内毒素含量的测定

本文采用鲎试剂对大肠杆菌（ＡＴＣＣ２５９２２）、伤寒杆菌、绿脓杆菌（ＡＴＣＣ７８５３）及它们的Ｌ型内毒素的含量进行测定。结果显示细菌型与细菌Ｌ型均具有内毒素,但细菌Ｌ型内毒素含量较细菌型低（约为１／３￣１／２）。因此,认为细菌Ｌ型仍有一定的致病性。     

Microbial Community Structures in Terrestrial Subsurface Sediments from the Southern Kanto Plain,Japan

Abstract

Microbial community structure reflects the surrounding natural environment and changes to that environment. Although the subsurface at 5–100?m depth is important for human activities and there are potential risks of environmental pollution in this region, there have been only a few reports of subsurface microbial community structures in terrestrial areas. We investigated the diversity and community compositions of Bacteria and Archaea in boring cores collected from various depths at three different sites in the southern Kanto Plain, Japan. The results of 16S rRNA gene amplicon sequencing using MiSeq showed that the microbial community composition varied with the geological unit. Proteobacteria (Alphaproteobacteria and Gammaproteobacteria) were dominant members within sediments accumulated during the Pleistocene in the Musashino Upland. In contrast, Acidobacteria and Chloroflexi characteristically appeared in the Holocene layers of the Arakawa Lowland. These data suggest that the subsurface microbial composition is controlled by the geological features of the sediments.     

Exploration of deep intraterrestrial microbial life: current perspectives

Intraterrestrial life has been found at depths of several thousand metres in deep sub-sea floor sediments and in the basement crust beneath the sediments. It has also been found at up to 2800-m depth in continental sedimentary rocks, 5300-m depth in igneous rock aquifers and in fluid inclusions in ancient salt deposits from salt mines. The biomass of these intraterrestrial organisms may be equal to the total weight of all marine and terrestrial plants. The intraterrestrial microbes generally seem to be active at very low but significant rates and several investigations indicate chemolithoautotrophs to form a chemosynthetic base. Hydrogen, methane and carbon dioxide gases are continuously generated in the interior of our planet and probably constitute sustainable sources of carbon and energy for deep intraterrestrial biosphere ecosystems. Several prospective research areas are foreseen to focus on the importance of microbial communities for metabolic processes such as anaerobic utilisation of hydrocarbons and anaerobic methane oxidation.     

Respiratory viral infection predisposing for bacterial disease: a concise review

Although bacterial superinfection in viral respiratory disease is a clinically well documented phenomenon, the pathogenic mechanisms are still poorly understood. Recent studies have revealed some of the mechanisms involved. Physical damage to respiratory cells as a result of viral infection may lead to opportunistic adherence of bacteria. Enhanced bacterial adherence by specific mechanisms has been documented for respiratory cells infected with influenza A virus, respiratory syncytial virus and adenovirus in both in vitro and in vivo models. To date, results of various experimental studies indicate that different mechanisms for increased bacterial adherence induced by viruses are operating for specific viral-bacterial combinations. In the present review, a number of key findings obtained during the past two decades is presented and discussed.     

Sequencing, cloning and expression of a β-1,4-mannanase gene, manA, from the extremely thermophilic anaerobic bacterium, Caldicellulosiruptor Rt8B.4

Abstract We report here the isolation of a Renibacterium salmoninarum DNA sequence capable of transforming a non-invasive Escherichia coli strain into a microorganism able to enter the fish cell line, CHSE-214. Immunofluorescence and electron microscopy techniques were used to assess the acquired invasive phenotype by HB101 E. coli cells, upon transformation with pPMV-189. This plasmid carries a 2282-bp R. salmoninarum DNA segment. The invasive phenotype is qonserved upon deletion of approximately 1000 bp at the 3' end of the insert. The remaining segment contains an ORF region encoding a putative protein of about 30 kDa.     

Characterization of the plant growth promoting bacterium,Enterobacter cloacae MSR1, isolated from roots of non-nodulating Medicago sativa

The aim of the present study was to characterize the endophytic bacterial strain designated MSR1 that was isolated from inside the non-nodulating roots of Medicago sativa after surface-sterilization. MSR1 was identified as Enterobacter cloacae using both 16S rDNA gene sequence analysis and API20E biochemical identification system (Biomerieux, France). Furthermore, this bacterium was characterized using API50CH kit (Biomerieux, France) and tested for antibacterial activities against some food borne pathogens. The results showed that E. cloacae consumed certain carbohydrates such as glycerol, d-xylose, d-maltose and esculin melibiose as a sole carbon source and certain amino acids such as arginine, tryptophan ornithine as nitrogen source. Furthermore, MSR1 possessed multiple plant-growth promoting characteristics; phosphate solubility, production of phytohormones acetoin and bioactive compounds. Inoculation of Pisum sativum with MSR1 significantly improved the growth parameters (the length and dry weight) of this economically important grain legume compared to the non-treated plants. To our knowledge, this is the first report addressing E. cloacae which exist in roots of alfalfa growing in Al-Ahsaa region. The results confirmed that E. cloacae exhibited traits for plant growth promoting and could be developed as an eco-friendly biofertilizer for P. sativum and probably for other important plant species in future.     

丛枝菌根真菌和根瘤菌互作对苜蓿根际土壤细菌群落结构的影响及PICRUSt功能预测分析

【背景】紫花苜蓿是优良的豆科牧草,可以与丛枝菌根(Arbuscular mycorrhizae,AM)真菌和根瘤菌形成共生关系,接种AM真菌和根瘤菌可以促进土壤氮、磷循环以及提高苜蓿产量。【目的】探究接种AM真菌和根瘤菌对苜蓿根际细菌群落结构和功能的影响。【方法】采集6个不同处理组苜蓿根际、非根际土壤样品,基于细菌16S rRNA基因V3?V4区进行高通量测序,分析比较不同处理组苜蓿根际、非根际土壤中细菌群落分布的规律,并采用PICRUSt软件对不同处理组间菌群功能进行预测。【结果】36个土壤样品中共检测到3 849个OTU,分属于50门59纲132目249科595属398种。其中主要的优势菌门为Proteobacteria (52.81%?81.46%)、Bacteroidetes (7.83%?19.68%)及Actinobacteria (2.21%?16.4%)。与不接种相比,接种根内球囊霉和摩西球囊霉分别提高了Gammaproteobacteria和Bacteroidia有益菌的丰度,接种根瘤菌提高了固氮菌(Alphaproteobacteria)的丰度。PICRUSt功能预测表明,细菌菌群共有35个子功能,菌群功能丰富,代谢为最主要的功能,并且接种根瘤菌可增加氨基酸代谢,从而有利于植株N素循环,而接种AM真菌可能对于N循环有一定的抑制作用,相比于单接种AM真菌,双接种AM真菌和根瘤菌处理组碳水化合物代谢更强,从而更有益于植株的氮、磷循环。【结论】接种AM真菌和根瘤菌可分别提高苜蓿根系与氮、磷循环有关的不同有益菌的丰度,从而更有益于植株的氮、磷循环,该结果为提高植株养分吸收、提高苜蓿产量以及菌肥开发利用提供了科学依据。     

Bacterial foraging algorithm with varying population

Most of evolutionary algorithms (EAs) are based on a fixed population. However, due to this feature, such algorithms do not fully explore the potential of searching ability and are time consuming. This paper presents a novel nature-inspired heuristic optimization algorithm: bacterial foraging algorithm with varying population (BFAVP), based on a more bacterially-realistic model of bacterial foraging patterns, which incorporates a varying population framework and the underlying mechanisms of bacterial chemotaxis, metabolism, proliferation, elimination and quorum sensing. In order to evaluate its merits, BFAVP has been tested on several benchmark functions and the results show that it performs better than other popularly used EAs, in terms of both accuracy and convergency.     

Bacterial corrosion of iron in seawater in situ, and in aerobic and anaerobic model systems

Abstract A screening of twenty-two marine isolates was made to examine their effects on corrosion of carbon steel ASTM A619. In batch cultures, sixteen of the isolates gave a lower corrosion than the control. Aerobic and anaerobic biofilm populations were formed by immersing iron coupons in natural seawater under aerobic and anaerobic conditions. The effects of the biofilms depended on a balance between the presence of oxygen and the type of population. An anaerobic population attached to the surface increased the corrosion rate if immersed in a suspension of Vibrio sp. DW1. The vibrio population probably 'protected' the anaerobic population from oxygen and may have provided nutrients, thereby creating conditions that allowed production of corrosive metabolites close to the metal. In contrast, coupons without a biofilm showed a decrease in the corrosion when immersed in the same vibrio suspension. The protective effect of a dense suspension of bacteria found earlier [5,6] was tested in situ in seawater. Iron coupons were immersed in dialysis bags with a suspension of Vibrio sp. DW1. Coupons immersed in dialysis bags with DW1 showed a lower degree of corrosion than coupons immersed in bags with seawater.     

Listeria monocytogenes Triggers the Cell Surface Expression of Gp96 Protein and Interacts with Its N Terminus to Support Cellular Infection

Listeria monocytogenes is an intracellular food-borne pathogen causing listeriosis in humans. This bacterium deploys an arsenal of virulence factors that act in concert to promote cellular infection. Bacterial surface proteins are of primary importance in the process of host cell invasion. They interact with host cellular receptors, inducing/modulating specific cellular responses. We previously identified Vip, a Listeria surface protein covalently attached to the bacterial cell wall acting as a key virulence factor. We have shown that Vip interacts with Gp96 localized at the surface of host cells during invasion and that this interaction is critical for a successful infection in vivo. To better understand the importance of Vip-Gp96 interaction during infection, we aimed to characterize this interaction at the molecular level. Here we demonstrate that, during infection, L. monocytogenes triggers the cellular redistribution of Gp96, inducing its exposure at the cell surface. Upon infection, Gp96 N-terminal domain is exposed to the extracellular milieu in L2071 fibroblasts and interacts with Vip expressed by Listeria. We identified Gp96 (Asp¹–Leu¹⁷⁰) as sufficient to interact with Vip; however, we also showed that the region Tyr¹⁷⁹–Leu³⁹⁰ of Gp96 is important for the interaction. Our findings unravel the Listeria-induced surface expression of Gp96 and the topology of its insertion on the plasma membrane and improve our knowledge on the Vip-Gp96 interaction during Listeria infection.