Studies on anaerobic proteolytic bacteria of Leh,India

Five anaerobic proteolytic bacteria were isolated from water bodies of Leh, India, where the ambient temperature varies from –25 to 25 °C. Isolates showed growth at all temperatures ranging from 5 to 37 °C except SPL-4 and SPL-5 which showed no growth at 5 °C. The cultures could grow and produce proteases on various protein substrates and the yield varied with the substrates. Two of the cultures showed the presence of spores. Acetate was the dominant VFA during hydrolysis of protein substrates.     

高效厌氧纤维素降解细菌的分离及酶特性研究

采用透明圈初筛和滤纸降解率复筛的方法从内蒙古绵羊瘤胃内容物中分离到高效厌氧纤维素降解细菌4株.通过形态学、生理生化反应、生态特性和遗传型的鉴定,所分离的4株菌WHQ、LYQ、LBG-1和NDF-3分别归为溶纤维丁酸弧菌(Butyrivibrio fibrisollvens)、黄色瘤胃球菌(Ruminococcus flavefaciens)、产琥珀酸丝状杆菌(Fibrobacter succinogenes)和解多糖梭菌(Clostridium polysaccharolyticum).测定了4株菌对滤纸的降解率,WHQ、LYQ、LBG-1和NDF-3的2周滤纸降解率分别为25.1%、14.3%、21.0%和20.6%.本研究同时对4株菌的滤纸酶活力、羧甲基纤维素酶活力和β-葡萄糖苷酶活力进行了测定.     

厌氧氨氧化菌的研究进展

厌氧氨氧化技术是一种新型生物脱氮技术,在废水处理中具有广泛的应用前途,对全球海洋的氮循环起着重要作用。由于反应中不需另加有机物、不消耗氧气、不会产生二次污染等优点,厌氧氨氧化技术受到格外关注。通常认为,厌氧氨氧化的机理在于厌氧氨氧化菌使氨和亚硝酸反应生成氮气。通过16SrRNA分子生物学方法已鉴定出该菌群属于分枝很深的浮霉菌,由于至今未能成功分离到纯的菌株,未正式命名,对其微生态环境以及生理生化特征也未能取得一致的意见。本文综述了国内外对厌氧氨氧化微生物的作用、分布、种类、生理生化特征等研究进展,认为厌氧氨氧化菌的分离纯化、生物特性、小生境等是今后的主要研究方向。     

Studies on some characteristics of hydrogen production by cell-free extracts of rumen anaerobic bacteria

Hydrogen production was studied in the following rumen anaerobes: Bacteroides clostridiiformis, Butyrivibrio fibrisolvens, Enbacterium limosum, Fusobacterium necrophorum, Megasphaera elsdenii, Ruminococcus albus, and Ruminococcus flavefaciens. Clostridium pasteurianum and Escherichia coli were included for comparative purposes. Hydrogen production from dithionite, dithionite-reduced methyl viologen, pyruvate, and formate was determined. All species tested produced hydrogen from dithionite-reduce methyl viologen, but only C. pasteurianum, B. clostridiiformis, E. limosum, and M. elsdenii produced hydrogen from dithionite. All species except E. coli produced hydrogen from pyruvate, but activity was low or absent in extracts of E. limosum, F. necrophorum, R. albus, and R. flavefaciens unless methyl viologen was added. Hydrogen was produced from formate only by E. coli, B. clostridiiformis, E. limosum, F. necrophorum, and R. flavefaciens. Extracts were subjected to ultracentrifugation in an effort to determine the solubility of hydrogenase. The hydrogenase of all species except E. coli appeared to be soluble, although variable amounts of hydrogenase activity were detected in the pellet. Treatment of extracts of the rumen microbial species with DEAE-cellulose resulted in loss ofhydrogen production from pyruvate. Activity was restored by the addition of methyl viologen. It is concluded that hydrogen production in these rumen microorganisms is similar to that in the saccharolytic clostridia.     

Corrinoids in anaerobic bacteria

Abstract C₁-metabolizing bacteria were analyzed for their corrinoids. The autotrophic phototrophe Chloroflexus aurantiacus contains predominantly the light-sensitive coenzyme B₁₂. The corrinoid could be teh prostethic group of a methylmalonyl-CoA mutase, which is involved in the CO₂ fixing reaction sequence from proplonyl-CoA to succinyl CoA. Methanobacterium thermoautotrophicum and Sporomusa ovata contain only traces of light-sensitive corrinoids, indicating that the demethylation reaction is favored, if these corrinoids are involved in methyl transfer reactions. The chemical structure of the unique p -cresolyl cobamide is specific for the acetogenic bacterium S. ovata , rather than the corrinoid 'factor III' for methanogenic bacteria.     

Biofilm-growing intestinal anaerobic bacteria

Sessile growth of anaerobic bacteria from the human intestinal tract has been poorly investigated, so far. We recently reported data on the close association existing between biliary stent clogging and polymicrobial biofilm development in its lumen. By exploiting the explanted stents as a rich source of anaerobic bacterial strains belonging to the genera Bacteroides, Clostridium, Fusobacterium, Finegoldia, Prevotella, and Veillonella, the present study focused on their ability to adhere, to grow in sessile mode and to form in vitro mono- or dual-species biofilms. Experiments on dual-species biofilm formation were planned on the basis of the anaerobic strains isolated from each clogged biliary stent, by selecting those in which a couple of anaerobic strains belonging to different species contributed to the polymicrobial biofilm development. Then, strains were investigated by field emission scanning electron microscopy and confocal laser scanning microscopy to reveal if they are able to grow as mono- and/or dual-species biofilms. As far as we know, this is the first report on the ability to adhere and form mono/dual-species biofilms exhibited by strains belonging to the species Bacteroides oralis, Clostridium difficile, Clostridium baratii, Clostridium fallax, Clostridium bifermentans, Finegoldia magna, and Fusobacterium necrophorum.     

Halophilic anaerobic fermentative bacteria

In hypersaline environments bacteria are exposed to a high osmotic pressure caused by the surrounding high salt concentrations. Halophilic microorganisms have specific strategies for balancing the osmotic pressure and surviving in these extreme conditions. Halophilic fermentative bacteria form taxonomically and phylogenetically a coherent group mainly belonging to the order Halanaerobiales. In this review, halophilic anaerobic fermentative bacteria in terms of taxonomy and phylogeny, special characteristics, survival strategies, and potential for biotechnological applications in a wide variety of branches, such as production of hydrogen, are discussed.     

Effect of solvents on obligately anaerobic bacteria

Growth of Acetobacterium woodii and Clostridium sporogenes was studied in the presence of water-immiscible solvents. Nitrogen purging, vacuum distillation or distillation under nitrogen were all suitable as methods to remove oxygen from the solvents, since growth rates and yields of A. woodii were unaffected in the presence of tetradecane which had been degassed by these methods. Varying the solvent volume from 20% to 80% of the culture volume had little effect on growth rate of A. woodii. A.woodii was relatively sensitive to organic solvents since growth was inhibited by alkanes with logP(octanol/water) values below 7.1. C. sporogenes was less solvent sensitive, since it grew without inhibition when the logP of the solvent was > or = 6.6. Nevertheless, both A. woodii and C. sporogenes were more sensitive to solvent polarity than aerobic bacteria.     

Citrate metabolism in anaerobic bacteria

Abstract The regulation of anaerobic citrate metabolism is very diverse among different groups of bacteria. In organisms like Streptococcus lactis and Clostridium sporosphaeroides which lack citrate synthase, the activity of its antagonistic enzyme, citrate lyase, need not be regulated. Many anaerobes like Rhodocyclus gelatinosus and Clostridium sphenoides are able to synthesize their own l -glutamate and contain citrate synthase. In these bacteria the activity of citrate metabolizing enzymes which are involved in a cascade system are under strict control. In Rc. gelatinosus activation/inactivation of citrate lyase is controlled by acetylation/deacetylation which is catalyzed by its corresponding regulatory enzymes, citrate lyase ligase and citrate lyase deacetylase. In C. sphenoides inactivation of citrate lyase is accomplished by deacetylation as well as by changing in the enzyme conformation. Activation of citrate lyase is catalyzed by citrate lyase ligase whose activity in addition is modulated by phosphorylation/dephosphorylation. Further, electron transport process also seems to play a role in the inactivation of citrate metabolizing enzymes in enteric bacteria.     

Unusual dehydrations in anaerobic bacteria

Abstract In amino acid fermenting anaerobic bacteria a set of unusual dehydratases is found which use 2-hydroxyacyl-CoA, 4-hydroxybutyryl-CoA or 5-hydroxyvaleryl-CoA as substrates. The extremely oxygen-sensitive 2-hydroxyacyl-CoA dehydratases catalysing the elimination of water from ( R )-lactyl-CoA to acryloyl-CoA or from ( R )-2-hydroxyglutaryl-CoA to glutaconyl-CoA contain iron-sulfur clusters as well as riboflavin and require additional activation by ATP. The dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA is catalysed by a moderately oxygen-sensitive enzyme also containing an iron-sulfur cluster and FAD. In all these reactions a non-activated C-H-bond at C₃ has to be cleaved by mechanisms not yet elucidated. The dehydration of 5-hydroxyvaleryl-CoA to 4-pentenoyl-CoA, however, has been characterised as a redox process mediated by enzyme-bound FAD. Finally, an iron-sulfur cluster-containing but pyridoxal-phosphate-independent l -serine dehydratase is described.     

厌氧氨氧化细菌的研究进展

厌氧氨氧化是指微生物在无氧条件下,以NO2-为电子受体,将NH4+氧化成N2的过程,该过程主要由浮霉菌门下的厌氧氨氧化细菌参与.厌氧氨氧化细菌广泛存在于海洋生态系统、淡水生态系统、陆地生态系统及其他一些特殊生境中,其在废水生物脱氮和地球氮循环中扮演着重要角色.本文从厌氧氨氧化细菌的发现历程、种类、特性、代谢途径、分布、...     

Effects of alkyltin compounds on hydrogen-oxidizing anaerobic bacteria

Methyl and butyltin compounds were inhibitory to all anaerobes examined, but there were great variations, depending on the specific alkyltin and bacterium. The methanogens were inhibited more strongly by methyl than by butyl derivatives; more than 50% inhibition occurred with 0.025–0.5 mM of the methyltins, whereas 0.16–1.8 mM butyltins were needed for the same level of inhibition; tri-butyltin was the least toxic.Methanosarcina barkeri was, in general, more resistant than theMethanococcus sp. andMethanobacterium bryantii. TheDesulfovibrio were more strongly inhibited by mono-methyltin than by di- and tri-methyl derivatives; butyltins were, in general, not so toxic. Mono-methyltin at 0.15 mM almost completely inhibited three of the sulfate reducers, butDesulfovibrio thermophilus required 0.7 mM for this level of inhibition. Tri-butyltin at 1.8 mM did not cause major inhibition, whereas mono- and di-butyltins were more inhibitory.Acetobacterium woodii was most affected by mono- and dimethyltins, and least by tri-methyltin and mono-butyltin. In contrast,Wollinella succinogenes was most affected by tri-methyltin. This study suggests several major groups of anaerobes thought to be involved in metal biocorrosion vary greatly in their response to alkyltins; most interesting is the relative insensitivity by methanogens and sulfate reducers to tri-butyltin, which is a major component in commercial antifouling paints. Our results differ considerably from those reported for aerobic microorganisms, which were found to be most affected by tributyltin.     

A novel anaerobic needle inoculator for strict obligate anaerobic bacteria

Summary An inoculating needle for picking and transferring colonies of strict anaerobic bacteria was built. A self-refilling syringe was adapted to carry a stainless steel needle within the cannula, and a tee junction allowed continuous flushing with dioxygen-free gas.     

Studies on methanol-oxidizing bacteria

Three methanol-oxidizing bacteria were isolated by enrichment culture technique from soil. Two of them werePseudomonas spp. The third one was obligate methylotroph. Their growth characteristics have been described. Cell-suspension experiments withPseudomonas RJ₁ suggest that methanol-, formaldehyde-, and formate-oxidizing enzymes were present. Formate-oxidizing enzyme was detected only fromPseudomonas RJ₁. It had a pH optimum of 7.0 and required nicotinamide adenine dinucleotide (NAD) for activity. Cyanide at 1 × 10⁻⁵ m concentration inhibited the enzyme activity completely.     

Oxygen tolerance in anaerobic pathogenic bacteria

A prerequisite for successful identification of anaerobic pathogenic bacteria from samples of clinical material is the method of cultivation. Currently, several methods of cultivation in anaerobic environment are used: cultivation in anaerobic box, anaerobic jar, and in nonrecurring cultivation system. Here, we determined the suitability of the above methods of cultivation using the estimation of the growth (diameters of colony size) of commonly isolated anaerobic pathogens (Bacteroides fragilis, Clostridium difficile, and Clostridium perfringens). The tested bacterial strains were exposed to atmospheric oxygen for various time periods and then they were cultivated using different anaerobic cultivation systems. Maximum growth differed, depending on the type of cultivation and the strain used. Thus, largest zone diameters, in the majority of measurements, were achieved in the anaerobic box. However, nonrecurring cultivation system seemed better in several cases; this applied to the cultivation of C. perfringens after 15, 30, and 60 min exposure to atmospheric oxygen as well as the cultivation of B. fragilis after 30 and 60 min of oxygen exposure. The cultivation in anaerobic box was the most convenient method for growth of C. difficile. In almost all cases, higher growth was observed in nonrecurring cultivation system than in the system of anaerobic jar. On the other hand, no significant differences were observed among these anaerobic cultivation systems which confirmed their applicability (taking into account some individual features concerning the optimization of cultivations) for identification of pathogenic anaerobes.     

厌氧氨氧化菌火山口结构

厌氧氨氧化(anaerobic ammonium oxidation, anammox)是微生物学、地质学和环境学领域的重要反应,厌氧氨氧化菌(anaerobic ammonium-oxidizing bacteria, AnAOB)是厌氧氨氧化的驱动器,探明AnAOB的生物学性状对厌氧氨氧化的应用具有重要意义。火山口结构是AnAOB的标志性微观结构,也是AnAOB的重要识别特征。由于迄今没有获得AnAOB纯培养物,相关研究进展缓慢。本文对AnAOB及其所归属的浮霉状菌的火山口结构研究进展作了综述,探讨了火山口结构的形态特征、生理功能和生态意义,得出以下结论:(1) AnAOB的火山口结构均匀分布在细胞表面,其直径约5 nm;(2) AnAOB的火山口结构推测向外可连通细胞外膜和内膜,向内可与厌氧氨氧化体膜相连,对于物质转运及转化具有重要意义;(3)火山口结构具有遗传稳定性,其形成可能与鞭毛脱落相关;(4) AnAOB的火山口结构可能通过促进细胞物质交流、信息通讯等在维持其生态位稳定方面起作用。