Studies on microbiologically influenced corrosion of SS304 by a novel manganese oxidizer,Bacillus flexus

A manganese oxidizing bacterium was isolated from the surface of steel scraps and biochemical tests and 16S rRNA sequencing analysis confirmed the isolate as Bacillus flexus. Potentiodynamic polarization curves showed ennoblement of open circuit potential, increased passive current, a lowering of breakdown potential, active re-passivation potential and enhanced cathodic current in the presence of B. flexus. Adhesion studies with B. flexus on SS304 specimens with different surface treatments demonstrated decreased adhesion on passivated and FeCl₃ treated specimens due to the removal of MnS inclusions. The present study provides evidence that surface treatment of stainless steels can reduce adhesion of this manganese oxidizing bacterium and decrease the probability of microbiologically influenced corrosion.     

广西湖润锰矿床的共生生金菌的分离与鉴定

从锰矿床中分离出一种氧化锰的细菌──共生生金菌,该菌嗜温、好氧,是一种化能有机营养型细菌,其适宜于pH6~8的环境中生长,生长具有周期性,与锰作用也表现出阶段性,是氧化锰的主要生物因素。     

一株碱性淀粉酶产生菌Bacillus flexus XJU-3的分离鉴定及酶学特性分析

[目的]从新疆石河子市一处碱性工业污水(pH11.0)分离﹑鉴定高产碱性淀粉酶菌株,并对其所产酶酶学特性进行研究.[方法]在碱性淀粉酶分离培养基上对所分离菌株进行筛选,分离到一株高产碱性淀粉酶菌株,并将其编号XJU-3.应用生理生化试验,脂肪酸含量,16S rDNA序列以及(G C) mol%含量等方法对菌株进行鉴定,同时对XJU-3所产碱性淀粉酶的生物学特性进行研究.[结果] XJU-3可在pH4.0～12.5的LB培养基上生长,最适生长温度37℃.16S rDNA序列构建的系统进化树表明XJU-3与Bacillus flexus类聚在一起,且序列同源性为99%.该菌产生的淀粉酶最适pH10.0,最适温度40℃,且在pH9.0～13.0内有较高活性和稳定性.Co2 和Mg2 能明显提高酶的活性.[结论] XJU-3被鉴定为Bacillus flexus,由于XJU-3与B. flexus DSM 1320T在尿素水解和优势脂肪酸含量上有差异,且具有宽范围pH耐受性,因此XJU-3被认为是B.flexus的一个新菌株.XJU-3所产的碱性淀粉酶酶学特性良好,具有极大的工业应用潜力.     

Measurement of charge transfer during bacterial adhesion to an indium tin oxide surface in a parallel plate flow chamber.

An experimental method is described for the measurement of charge transfer during bacterial adhesion in situ to a transparent, semiconducting indium tin oxide (ITO) coated glass plate in a parallel plate flow chamber. Bacterial adhesion is measured simultaneously with either the electric potential or the capacitance of the surface. Initial bacterial adhesion was accompanied by a change in electric potential of the surface with no measurable change in capacitance. Consequently, it can be assumed that the change in electric potential of the surface is due to charge transfer between bacteria and the surface, and it can be calculated that, on average, a charge of about 10(-14) C per bacterium is exchanged during initial adhesion, which corresponds to only several percent of the total surface charge of a bacterium. Charge transfer could either be to or from the bacterial cell surface, dependent on the bacterial strain involved and the ionic strength used.     

Biomineralisation of manganese on titanium surfaces exposed to seawater

A 2-year long study was carried out to isolate and characterise various bacterial species present in the biofilm formed on titanium surfaces exposed to seawater and to assess the manganese oxidizing potential of the marine isolates. The amount of manganese present in the biofilm was also measured using atomic absorption spectrometry (AAS). The results showed that titanium was susceptible to biofouling. More than 50% of the culturable marine bacterial isolates were capable of bringing about oxidation of Mn(II). All these manganese oxidizing bacteria were heterotrophic. Autotrophic manganese oxidizing bacteria such as Leptothrix was not isolated in the present study. The AAS results confirmed that the manganese content in the biofilms increased with increasing exposure time. Hence, the study indicates that the titanium surfaces when exposed to seawater were colonised by a large number of heterotrophic bacteria, which have the ability of bringing about biomineralisation of manganese.     

A light-dependent mechanism for massive accumulation of manganese in the photosynthetic bacterium Synechocystis sp. PCC 6803

Manganese is an essential micronutrient for many organisms. Because of its unique role in the water oxidizing activity of photosystem II, manganese is required for photosynthetic growth in plants and cyanobacteria. Here we report on the mechanism of manganese uptake in the cyanobacterium Synechocystis sp. PCC 6803. Cells grown in 9 microM manganese-containing medium accumulate up to 1 x 10(8) manganese atoms/cell, bound to the outer membrane (pool A). This pool could be released by EDTA treatment. Accumulation of manganese in pool A was energized by photosynthetic electron flow. Moreover, collapsing the membrane potential resulted in the immediate release of this manganese pool. The manganese in this pool is mainly Mn(II) in a six-coordinate distorted environment. A distinctly different pool of manganese, pool B ( approximately 1.5 x 10(6) atoms/cell), could not be extracted by EDTA. Transport into pool B was light-independent and could be detected only under limiting manganese concentrations (1 nM). Evidently, manganese uptake in Synechocystis 6803 cells occurs in two steps. First, manganese accumulates in the outer membrane (pool A) in a membrane potential-dependent process. Next, manganese is transported through the inner membrane into pool B. We propose that pool A serves as a store that allows the cells to overcome transient limitations in manganese in the environment.     

Streptococcus thermophilus and its biosurfactants inhibit adhesion by Candida spp. on silicone rubber.

The adhesion of yeasts, two Candida albicans and two Candida tropicalis strains isolated from naturally colonized voice prostheses, to silicone rubber with and without a salivary conditioning film in the absence and presence of adhering Streptococcus thermophilus B, a biosurfactant-releasing dairy isolate, was studied. Coverage of 1 to 4% of the surface of silicone rubber substrata with adhering S. thermophilus B gave significant reductions in the initial yeast adhesion regardless of the presence of a conditioning film. Mechanistically, this interference in yeast adhesion by S. thermophilus B was not due to direct physical effects but to biosurfactant release by the adhering bacteria, because experiments with S. thermophilus B cells that had released their biosurfactants prior to adhesion to silicone rubber and competition with yeasts did not show interference with initial yeast adhesion. The amounts of biosurfactants released were highest for mid-exponential- and early-stationary-phase bacteria (37 mg.g of cells-1 [dry weight]), but biosurfactants released by stationary-phase bacteria (14 mg.g of cells-1 [dry weight]) were the most surface active. The crude biosurfactants released were mixtures of various components, with a glycolipid-like component being the most surface active. A lipid-enriched biosurfactant fraction reduced the surface tension of an aqueous solution to about 35 mJ.m-2 at a concentration of only 0.5 mg.ml-1. The amount of biosurfactant released per S. thermophilus B cell was estimated to be sufficient to cover approximately 12 times the area of the cross section of the bacterium, making biosurfactant release a powerful defense weapon in the postadhesion competition of the bacterium with microorganisms such as yeasts. Preadsorption of biosurfactants to the silicone rubber prior to allowing yeasts to adhere was as effective against C. albicans GB 1/2 adhesion as covering 1 to 2% of the silicone rubber surface with adhering S. thermophilus B, but a preadsorbed biosurfactant layer was less effective against C. tropicalis GB 9/9.     

Mechanism of microbial flotation using Thiobacillus ferrooxidans for pyrite suppression

Microbial desulfurization might be developed as a new process for the removal of pyrite sulfur from coal sluries such as coal-water mixture (CWM). An application of iron-oxidizing bacterium Thiobacillus ferrooxidans to flotation would shorten the periods of the microbial removal of pyrite from some weeks by leaching methods to a few minutes. The floatability of pyrite in flotation was mainly reduced by T. ferrooxidans itself rather than by other microbial substances in bacterial culture as additive of flotation liquor. Floatability was suppressed within a few seconds by bacterial contact. The suppression was proportional to increasing the number of cells observed between bacterial adhesion and the suppression of floatability. If 25% of the total pyrite surface area covered with the bacteria, pyrite floatability would be completely depressed. Bacteria that lost their iron-oxidizing activities by sodium cyanide treatment were also able to adhere to pyrite and reduced pyrite floatability as much as normal bacteria did. Thiobacillus ferrooxidans ATCC 23270, T-1, 9, and 11, which had different iron-oxidizing abilities, suppressed floatability to similar-levels. The oxidizing ability of bacteria did not influence the suppressing effect. These results showed the mechanism of the suppression of pyrite floatability by bacteria. Quick bacterial adhesion to pyrite induced floatability suppression by changing the surface property from hydrophobic. The quick adhesion of the bacterium was the novel function which worked to change the surface property of pyrite to remove it from coal. (c) 1993 John Wiley & Sons, Inc.     

The extracellular proteome of Bifidobacterium animalis subsp. lactis BB-12 reveals proteins with putative roles in probiotic effects

Probiotics are live microorganisms that exert health-promoting effects on the human host, as demonstrated for numerous strains of the genus Bifidobacterium. To unravel the proteins involved in the interactions between the host and the extensively used and well-studied probiotic strain Bifidobacterium animalis subsp. lactis BB-12, proteins secreted by the bacterium, i.e. belonging to the extracellular proteome present in the culture medium, were identified by 2-DE coupled with MALDI-TOF MS. Among the 74 distinct proteins identified, 31 are predicted to carry out their physiological role either outside the cell or on its surface. These proteins include solute-binding proteins for oligosaccharides, amino acids and manganese, cell wall-metabolizing proteins, and 18 proteins that have been described to interact with human host epithelial cells or extracellular matrix proteins. The potential functions include binding of plasminogen, formation of fimbriae, adhesion to collagen, attachment to mucin and intestinal cells as well as induction of immunomodulative response. These findings suggest a role of the proteins in colonization of the gastrointestinal tract, adhesion to host tissues, or immunomodulation of the host immune system. The identification of proteins predicted to be involved in such interactions can pave the way towards well targeted studies of the protein-mediated contacts between bacteria and the host, with the goal to enhance the understanding of the mode of action of probiotic bacteria.     

Acidification of the Culture Medium by Products of Glucose Metabolism Inhibits the Synthesis of Heterologous Extracellular α-amylase by Bacillus subtilis 168

Applied Biochemistry and Microbiology - The synthesis of α-amylase AmyM3 from B. flexus 406 in the recombinant strain B. subtilis 168-28 was significantly repressed during submerged...     

The influence of environmental factors on the rate and extent of stainless steel ennoblement mediated by manganese‐oxidizing biofilms

The increase in the open circuit potential of passive metals in natural waters due to biofilm formation at the metal surface, termed ennoblement, has been reported for nearly 30 years. Although its occurrence is undoubtedly associated with microbial colonization, the underlying mechanism of ennoblement remains controversial. Recent work produced in the authors’ laboratory has provided convincing experimental evidence that ennoblement can be caused by deposition of biomineralized manganese produced by manganese‐oxidizing biofilms. The purpose of this study was to determine the effects of environmental factors on the rate and extent of ennoblement of 316L stainless steel exposed to natural waters. This was accomplished by exposing corrosion coupons to four freshwater systems over a 4‐yearperiod. The rate and extent of ennoblement observed in these locations was correlated with dissolved manganese concentrations, the mass of accumulated manganese oxides, organic carbon concentration, dissolved oxygen concentration, flow, conditions, temperature, and pH in these environments.     

锰氧化菌Bacillus sp. MK3-1的Mn(Ⅱ)氧化特性和除锰能力研究

锰氧化微生物能够将可溶的Mn(II)氧化为不溶的锰氧化物沉淀, 因此在生物除锰研究上具有重要的应用价值。本研究从锰污染土壤中分离到一株锰氧化菌Bacillus sp. MK3-1, 该菌对MnCl2有较高抗性, 其最低抑制浓度(Minimal inhibitory concentration, MIC)为20 mmol/L。实验表明该菌在培养基中Mn(Ⅱ)的去除率高达96%, 同时将其制成固体包埋菌剂应用于含0.15 mmol/L的MnCl2水溶液实验, 结果表明其仍然具有稳定的除锰能力, 去除率为87.12%, 使溶液的终锰浓度符合国家排放标准。扫描电子显微镜观察和能谱分析实验表明, 实验产生的锰氧化物均匀地分布在Bacillus sp. MK3-1的细胞表面, 细胞表面含锰量为19.60% (W/W)。用简并引物扩增目前被认为催化锰氧化的多铜氧化酶基因mnxG, 获得了903 bp的基因片段, 其基因产物与已报道的多铜氧化酶具有86%的同源性。     

Semiquantitative Performance and Mechanism Evaluation of Carbon Nanomaterials as Cathode Coatings for Microbial Fouling Reduction

In this study, we examine bacterial attachment and survival on a titanium (Ti) cathode coated with various carbon nanomaterials (CNM): pristine carbon nanotubes (CNT), oxidized carbon nanotubes (O-CNT), oxidized-annealed carbon nanotubes (OA-CNT), carbon black (CB), and reduced graphene oxide (rGO). The carbon nanomaterials were dispersed in an isopropyl alcohol-Nafion solution and were then used to dip-coat a Ti substrate. Pseudomonas fluorescens was selected as the representative bacterium for environmental biofouling. Experiments in the absence of an electric potential indicate that increased nanoscale surface roughness and decreased hydrophobicity of the CNM coating decreased bacterial adhesion. The loss of bacterial viability on the noncharged CNM coatings ranged from 22% for CB to 67% for OA-CNT and was dependent on the CNM dimensions and surface chemistry. For electrochemical experiments, the total density and percentage of inactivation of the adherent bacteria were analyzed semiquantitatively as functions of electrode potential, current density, and hydrogen peroxide generation. Electrode potential and hydrogen peroxide generation were the dominant factors with regard to short-term (3-h) bacterial attachment and inactivation, respectively. Extended-time electrochemical experiments (12 h) indicated that in all cases, the density of total deposited bacteria increased almost linearly with time and that the rate of bacterial adhesion was decreased 8- to 10-fold when an electric potential was applied. In summary, this study provides a fundamental rationale for the selection of CNM as cathode coatings and electric potential to reduce microbial fouling.     

Bacteroides fragilis interferes with iNOS activity and leads to pore formation in macrophage surface

Bacteroides fragilis is the anaerobe most commonly recoverable from clinical specimens. The wide genetic diversity of this bacterium related with virulence potential is still an open question. In this study, we analyzed the morphological aspects and microbicide action of M? during interactions with B. fragilis. A filamentous cytoplasm content release and a different actin organization colocalized with iNOS were detected. It was also possible to observe the reduction of NO production in the same conditions. The scanning electron microscopy showed the formation of pore-like structures in the surface of macrophages in the bacterial presence and by transmission electron microscopy we could observe the extrusion of cytoplasm contents as well as the condensation of chromatin in the nucleus periphery. These data suggest the existence of an inhibitory mechanism developed by B. fragilis strains for one of the macrophage microbicide actions.     

Modulation of the hydrophobicity of glutamine synthetase by mixed-function oxidation

Oxidative modification of Escherichia coli glutamine synthetase renders the enzyme susceptible to proteolytic degradation by a specific protease purified from the bacterium; native enzyme is not a substrate for the protease. A model oxidizing system consisting of ascorbate, iron, and oxygen was used to generate a series of glutamine synthetases of increasing oxidative modification. We assessed the effect of oxidative modification on the surface hydrophobicity of the glutamine synthetases, utilizing hydrophobic chromatography on a phenyl matrix. Initial exposure to the oxidizing system caused inactivation of the enzyme and generated a protein that was more hydrophilic than the native form; it was not a substrate for the protease. Continued exposure to the oxidizing system yielded a protein with additional oxidative modification. This form was distinctly more hydrophobic than the native form and it was very susceptible to proteolytic attack by the purified protease. Thus, oxidative modification modulates the surface hydrophobicity of glutamine synthetase, and this modulation can control susceptibility to proteolysis.     

Infections with the chlamydia-like microorganism Simkania negevensis,a possible emerging pathogen

Although evidence for the existence of numerous chlamydia-like microorganisms has been discovered in both environmental samples and clinical specimens, very few have been grown in vitro, and little is known of their pathogenic potential. Of all such organisms, Simkania negevensis is probably the most extensively studied. This review summarizes current knowledge about this intracellular bacterium, focusing especially on human infections.     

锰氧化细菌的生理生态功能与作用机制研究进展

锰的生物地球化学循环过程与全球尺度的营养元素循环紧密联系,是影响全球生态平衡及气候变化的重要因素之一。在自然界中,锰元素主要以氧化锰和含氧酸盐的矿物形式存在,近年来的研究观点普遍认为细菌介导的氧化作用是自然环境中锰氧化物形成的主要原因。锰氧化细菌广泛分布于海洋、锰矿土壤等生态系统,近期在植物微生态系统中也被发现,其生理生态功能未知。细菌的锰氧化过程是一个复杂的过程,多铜氧化酶和过氧化物(氢)酶是参与该过程的主要酶类,但关于其催化机制的认识尚不成熟。本综述系统探讨锰氧化细菌的种类和分布、细菌锰氧化作用的生理生态功能、参与细菌锰氧化作用的功能酶及其分子机制,总结这一研究领域所取得的成果和仍未解决的科学问题,并对今后的发展方向进行展望。     

Anti-biofilm potential of a glycolipid surfactant produced by a tropical marine strain of Serratia marcescens

A tropical marine bacterium isolated from the hard coral, Symphyllia sp. was identified as Serratia marcescens on the basis of morphological, biochemical and 16S rDNA analysis. The bacterium showed antimicrobial activity towards the pathogens Candida albicans and Pseudomonas aeruginosa and the marine biofouling bacterium Bacillus pumilus. S. marcescens displayed biosurfactant activity as evidenced by drop collapse, blood hemolysis and surface tension reduction (52.0-27 mN m(-1)). The active compound was purified by solvent extraction and silicic acid chromatography. Characterization was by thin layer chromatography, gas chromatography mass spectroscopy (GC-MS), Fourier transform infrared (FTIR) spectroscopy and (1)H as well as (13)C nuclear magnetic resonance (NMR) analysis. The surfactant was found to be a glycolipid composed of glucose and palmitic acid. The glycolipid prevented adhesion of C. albicans BH, P. aeruginosa PAO1 and B. pumilus TiO1. The glycolipid also disrupted preformed biofilms of these cultures in microtitre plates. Confocal laser scanning microscopy and electron microscopy confirmed the effective removal of biofilms from glass surfaces. The glycolipid derived from S. marcescens could thus serve as a potential anti-biofilm agent.     

A method for cultivation of microorganisms oxidizing iron and manganese in bottom sediments of Lake Baikal

Methods for cultivation of microorganisms oxidizing iron and manganese in bottom sediments of Lake Baikal were tested. Bacteria were grown on selective media with a characteristic accumulation of metal oxides. The morphology and developmental patterns of the isolated microbial group were studied. The studied sediment core was used to isolate 42 strains of bacteria oxidizing iron and manganese. The cultivated bacteria were confined to the upper sediment layers (down to 11 cm) and their abundance depended on sediment type and redox conditions.     

Adhesion of cells to polystyrene surfaces

The surface treatment of polystyrene, which is required to make polystyrene suitable for cell adhesion and spreading, was investigated. Examination of surfaces treated with sulfuric acid or various oxidizing agents using (a) x-ray photoelectron and attenuated total reflection spectroscopy and (b) measurement of surface carboxyl-, hydroxyl-, and sulfur-containing groups by various radiochemical methods showed that sulfuric acid produces an insignificant number of sulfonic acid groups on polystyrene. This technique together with various oxidation techniques that render surfaces suitable for cell culture generated high surface densities of hydroxyl groups. The importance of surface hydroxyl groups for the adhesion of baby hamster kidney cells or leukocytes was demonstrated by the inhibition of adhesion when these groups were blocked: blocking of carboxyl groups did not inhibit adhesion and may raise the adhesion of a surface. These results applied to cell adhesion in the presence and absence of serum. The relative unimportance of fibronectin for the adhesion and spreading of baby hamster kidney cells to hydroxyl-rich surfaces was concluded when cells spread on such surfaces after protein synthesis was inhibited with cycloheximide, fibronectin was removed by trypsinization, and trypsin activity was stopped with leupeptin.