An outer membrane protein A (ompA) homologue from the photosynthetic purple sulfur bacterium Allochromatium vinosum

A 991 bp DNA fragment, consisting of a 225 amino acid reading frame homologous to outer membrane protein coding ompA gene, was cloned from a purple sulfur bacterium Allochromatium vinosum. The homology analysis revealed up to 51% similarity to other bacterial species. The absence of branching within diazotrophs or other taxonomically related groups shows the structural importance of the protein regardless of the metabolism and evolution of the species.     

The potential for beach sand to serve as a reservoir for Escherichia coli and the physical influences on cell die-off

AIMS: The Escherichia coli burden at a Great Lakes urban beach was evaluated during the summer months to determine if sand served as a reservoir for E. coli, and if there was evidence of cell replication in situ. Field and laboratory studies investigated the effects of moisture, temperature and UV on E. coli densities in the sand. METHODS AND RESULTS: Sand samples (n = 481) were collected across three distinct transects of the beach, the top, a middle streamline, and the berm, over 15 sample days. The highest levels were found in the middle streamline, which was affected by stormwater discharge from nearby outfalls and roosting gulls; daily geometric mean levels of these seven sites ranged from 6700 to 40,900 CFU per 100 g of sand. Escherichia coli levels were greatest in samples with moisture levels between 15% and 19%, and were significantly higher than 0-4 and 20-24% ranges (P < 0.05). Pre- and post-rain samples at the beach demonstrated an increase in E. coli levels nearly 100-fold within 30 min, suggesting sand washout as a major mechanism for loading of E. coli into the beach waters. Rep PCR analysis of 160 isolates obtained from eight sites demonstrated that 21% of the isolates fell into one of the six clonal patterns, suggesting that bacteria may be able to replicate and possibly colonize beach sand. Sand field plots inoculated with E. coli cells containing pGFPuv that expresses GFP (green fluorescent protein) as a marker showed an initial two- to 100-fold increase at 24 h, depending on the temperature condition. The sand appeared to provide considerable protection from UV exposure as no significant difference was seen in cell densities within the first 2-4 cm of sand between exposed and unexposed plots (P < 0.05). CONCLUSIONS: Beach sand may act as a reservoir for E. coli. Replication of cells appears to be one possible contributing factor to the persistently high levels, as indicated by both field studies and laboratory studies, and warrants further investigation. Moisture content of sand may also be a determinant of cell persistence in the sand environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Escherichia coli is used as an indicator organism for faecal pollution at most Great Lakes coastal beaches; therefore, a better understanding of how E. coli might survive, or possibly replicate, in the environment would improve interpretation of beach monitoring results.     

Bioprospection and secondary metabolites profiling of marine Streptomyces levis strain KS46

The quest for novel broad spectrum bioactive compounds is needed continuously because of the rapid advent of pathogenic multi drug resistant organisms. Actinomycetes, isolated from unexplored habitats can be a solution of this problem. The motive of this research work was isolation of actinomycetes having potential antimicrobial activities from unexplored regions of Devbag and Tilmati beach. The isolated actinomycetes were screened against pathogenic microbes for antimicrobial activities through cross streak method. Enzyme production activity was checked for these actinomycetes for amylase, protease, cellulase and lipase enzymes. Further antimicrobial activity of ethyl acetate extract of the potent strain KS46 was performed. The strain KS46 was identified with 16S rRNA gene sequencing and secondary structure was analysed. Gas chromatography–Mass spectrometry (GC–MS) profiling was conducted to ascertain the presence of bioactive metabolites in the ethyl acetate extract. The collected samples were pre-treated and 70 actinomycetes were isolated. The Streptomyces sp. strain KS46 showed the best antimicrobial activity in primary screening. Ethyl acetate extract of the strain KS46 revealed antimicrobial activity against S. aureus, B. subtilis, B. cereus, E. faecalis, K. pneumoniae, E. coli, S. flexneri, C. albicans and C. glabrata. The 16S rRNA gene sequencing identified the strain KS46 as Streptomyces levis strain KS46. The GC–MS metabolite profiling of the ethyl acetate extract revealed the availability of 42 compounds including fatty acid esters, fatty acid anhydrides, alkanes, steroids, esters, alcohols, carboxylic ester, etc. having antibacterial, antifungal, antiproliferative, antioxidant activities. This study indicated that Devbag and Tilmati beaches being untapped habitats have enormous diversity of promising antimicrobial metabolite producing actinomycetes. Therefore, further exploration should be carried out to characterize the potential actinomycetes, which can be optimistic candidates for generation of novel antimicrobial drugs.     

付里叶变换偏振红外光谱法研究紫膜LB膜内菌紫质的取向

用付里叶变换偏振红外法测量了紫膜LB膜内菌紫质的酰胺Ⅰ、Ⅱ和A带的二色性,计算了菌紫质的α-螺旋取向.实验表明,紫膜内菌紫质的α-螺旋轴同膜法线的平均夹角为13°,即与膜平面的平均夹角为77°.     

环境对沼泽红假单胞菌基因型的影响

<正>紫色光合细菌是不产氧光合细菌的一个重要分支,包括紫色非硫细菌和紫色硫细菌。其中紫色非硫细菌具有极其丰富的代谢模式,可进行光能异养、光能自养和化能异养生长,其代谢的多样性使得它们广泛存活于不同的生态系统中,如土壤、湖泊、海洋及底泥等[1-2]。沼泽红假单胞菌(Rhodopseudomonas palustris)是紫     

几株红假单胞菌属细菌的表观特征及其遗传多样性研究

采用变性梯度胶电泳(DGGE)分析方法和传统的表型特征研究方法、化学方法、核酸杂交方法等技术对14株紫色非硫细菌进行了多相研究。它们均具有红假单胞菌属(Rhodopseudomonas)的基本特征：具片层状光合内膜结构,出芽分裂,含细菌叶绿素α和正常的螺菌黄素等。根据形态大小、黑暗条件下能否形成好氧菌落及碳源利用上的差异可将14株菌分为T群和gc群两群。用一对引物341f～906r扩增3株标准菌株Rps.palustris ATCC 17001、Rps.rutila R1、Rps.julia ATCC 51105和14株分离株的16S rRNA基因片断,作DGGE分析,结果发现,17株菌中有5个遗传型：gc型、R1型、T型、pal型、jul型。3个标准菌株分别是R1型、pal型、jul型,而14株分离菌株除包括R1型外,另有2个新的遗传型：T型和gc型。几个代表菌株的总DNA的杂交结果表明,T型和gc型可能代表2个新的种群。     

紫细菌光合机构及光合作用基因的表达调控

紫细菌是研究细菌光合作用的重要生物.介绍了紫细菌光合机构捕光色素蛋白复合体Ⅰ(light-harvestingⅠ)、捕光色素蛋白复合体Ⅱ(1ight-harvesting Ⅱ)和光化学反应中心(reaction center)的结构,并探讨了其光合作用基因的转录调控机制,重点阐述了PpsR/AppA系统对紫细菌光合作用基因的转录调控.     

紫甘薯花色苷色素的抑菌作用研究

本文研究了紫甘薯花色苷色素抑制大肠杆菌、金黄色葡萄球菌、啤酒酵母和黑曲霉的作用及机理.结果表明:紫甘薯花色苷色素对大肠杆菌及金黄色葡萄球菌均有抑制作用,并与其浓度呈正相关,而对啤酒酵母和黑曲霉无抑制作用.透射电镜观察和大肠杆菌生长曲线表明,该色素的抑菌作用可能是通过增强细胞膜的通透性,使细胞异常生长,抑制对数生长期的细胞分裂,使细胞质稀薄、细胞解体.SDS-PAGE分析表明,紫甘薯花色苷对大肠杆菌蛋白表达影响不明显,未见特征性条带的消失,仅对部分蛋白质合成量有影响.     

时空监测海水浴场粪大肠菌群和人类腺病毒方法的探讨（英文稿）

[目的]人类腺病毒(40/41)与人类急性胃肠炎显著相关,被用作娱乐水体中人类病毒污染的指示生物.粪大肠菌群(FC)作为传统的细菌指示生物,用来估计水环境中病原微生物的潜在风险.了解水传播的病原微生物的时空分布对公众健康和疾病的预防具有十分重要的意义.[方法]于2008年5月到10月,在中国10个典型海水浴场共采集30个表层海水样品,分别用定量PCR和细胞培养的方法分析人类腺病毒和FC.[结果]腺病毒的含量为1.7×106-1.1×108基因拷贝/L,其阳性检出率为30％,而普通PCR的阳性检出率为26.7％.其中7个海水浴场的FC超出了景观娱乐水质标准(2 000 CFU/L).时间分布趋势表明,人类腺病毒从8月份到10月份的污染较其他月份严重(P＜0.05).在该实验条件下,不论是在同一浴场的不同站位还是在不同浴场,腺病毒的空间分布差异都不明显(P＞0.05).同样,FC在不同浴场的时空分布也无明显差异(P＞0.05),但是其分布与离岸距离的远近显著相关(P＜0.05).此外,在我们所研究的浴场,细菌和病毒这两种指示生物之间并没有相关性.[结论]为避免在游泳季节胃肠道疾病的大规模爆发,必须加强卫生设施建设和肠道细菌、病毒两种指示生物的监测.     

岸滩粪便污染指示菌来源与影响因素研究进展

粪便污染指示菌(Fecal Indicator Bacteria,FIB),如大肠杆菌、肠球菌和耐热大肠菌等是用于指示水体中污染程度的微生物,但近年来的研究表明岸滩逐步成为FIB的重要储存库。微生物源示踪技术(MicrobialSourceTracking,MST)等方法被广泛应用于溯源岸滩FIB污染,但FIB进入岸滩环境后的生消机制尚不明确,因此影响FIB在岸滩上生存、消亡的各类因素仍是目前研究的热点。基于此,本文综述了岸滩生态系统中FIB的来源,同时结合国内外研究进展分析了影响FIB生存的非生物因素、生物因素及间隙流动等其他影响因素,并针对岸滩环境中FIB对人体健康的潜在风险提出相关建议,以期降低游客的患病风险,保障公共健康安全。