Numerical Data Concerning the Sensitivity of Anaerobic Bacteria to Oxygen

Upon comparison of results obtained from growing eight different species of anaerobic bacteria in deep agar under two and three atm of pure oxygen with results of growing them in air under atomospheric pressure, it appears possible that the old terms of "microaerophobic," "very strict anaerobe," and "microaerophilic" can be replaced by precise values corresponding to the size of the inhibition zone produced by oxygen under various pressures when the bacteria are grown in a solid medium. The simultaneous effect of the dilution of the inoculum and the pressure of oxygen used was determined with the help of an electronic computer according to the standard multiple regression method. Two indices have been worked out which express the sensitivity of the species at different oxygen pressures when varying numbers of anaerobic bacteria are used: X sp, which is the size in millimeters of the inhibition zone when 1:10 dilutions of the culture are grown under pure oxygen at atmospheric pressure (lp=0), and B sp, which is the result of multiplying by 1.43 the difference in size of inhibition zone when 1:10 dilutions of the culture are grown under atmospheric air (lp = -0.7) and under pure oxygen at 1 atm absolute.     

Oxygen Sensitivity of Various Anaerobic Bacteria

Anaerobes differ in their sensitivity to oxygen, as two patterns were recognizable in the organisms included in this study. Strict anaerobes were species incapable of agar surface growth at pO(2) levels greater than 0.5%. Species that were found to be strict anaerobes were Treponema macrodentium, Treponema denticola, Treponema oralis n. sp., Clostridium haemolyticum, Selenomonas ruminatium, Butyrivibrio fibrisolvens, Succinivibrio dextrinosolvens, and Lachnospira multiparus. Moderate anaerobes would include those species capable of growth in the presence of oxygen levels as high as 2 to 8%. The moderate anaerobes could be exposed to room atmosphere for 60 to 90 min without appreciable loss of viability. Species considered as moderate anaerobes were Bacteroides fragilis, B. melaninogenicus, B. oralis, Fusobacteria nucleatum, Clostridium novyi type A, and Peptostreptococcus elsdenii. The recognition of at least two general types of anaerobes would seem to have practical import in regard to the primary isolation of anaerobes from source material.     

Tolerance and Metabolic Response of Acetogenic Bacteria toward Oxygen

The acetogens Sporomusa silvacetica, Moorella thermoacetica, Clostridium magnum, Acetobacterium woodii, and Thermoanaerobacter kivui (i) grew in both semisolid and liquid cultivation media containing O₂ and (ii) consumed small amounts of O₂. Low concentrations of O₂ caused a lag phase in growth but did not alter the ability of these acetogens to synthesize acetate via the acetyl coenzyme A pathway. Cell extracts of S. silvacetica, M. thermoacetica, and C. magnum contained peroxidase and NADH oxidase activities; catalase and superoxide dismutase activities were not detected.     

Anaerobic Ammonia-Oxidizing Bacteria and Related Activity in Baltimore Inner Harbor Sediment

The discovery of bacteria capable of anaerobic ammonia oxidation (anammox) has generated interest in understanding the activity, diversity, and distribution of these bacteria in the environment. In this study anammox activity in sediment samples obtained from the Inner Harbor of Baltimore, Md., was detected by ¹⁵N tracer assays. Anammox-specific oligonucleotide primer sets were used to screen a Planctomycetales-specific 16S rRNA gene library generated from sediment DNA preparations, and four new anammox bacterial sequences were identified. Three of these sequences form a cohesive new branch of the anammox group, and the fourth sequence branches separately from this group. Denaturing gradient gel electrophoresis analysis of sediment incubated with anammox-specific media confirmed the presence of the four anammox-related 16S rRNA gene sequences. Evidence for the presence of anammox bacteria in Inner Harbor sediment was also obtained by using an anammox-specific probe in fluorescence in situ hybridization studies. To our knowledge, this is the first report of anammox activity and related bacterial 16S rRNA gene sequences from the Chesapeake Bay basin area, and the results suggest that this pathway plays an important role in the nitrogen cycle of this estuarine environment. Furthermore, the presence of these bacteria and their activity in sediment strengthen the contention that anammox-related Plactomycetales are globally distributed.     

Relations of Oligotrophic Bacteria to Oxygen

Polluted air and the derived photochemical smog are the sources of free radicals in the atmosphere. Organic peroxides present in the smog mediate formation of peroxide radical. Oxygen species are formed by purely physical mechanisms, for instance, energy consumption converts molecular oxygen to an excited singlet state. Six active oxygen species are known: ozone, atomic oxygen, perhydroxyl, superoxide, and singlet oxygen. Singlet oxygen is the most harmful oxygen product for living cells, while hydrogen peroxide is the least harmful. Molecular oxygen is hardly toxic for prokaryotes due to an efficient protection of microbial cells by specific enzymes. This work experimentally confirms the harmlessness of molecular oxygen.     

Adhesion of Biodegradative Anaerobic Bacteria to Solid Surfaces

In order to exploit the ability of anaerobic bacteria to degrade certain contaminants for bioremediation of polluted subsurface environments, we need to understand the mechanisms by which such bacteria partition between aqueous and solid phases, as well as the environmental conditions that influence partitioning. We studied four strictly anaerobic bacteria, Desulfomonile tiedjei, Syntrophomonas wolfei, Syntrophobacter wolinii, and Desulfovibrio sp. strain G11, which theoretically together can constitute a tetrachloroethylene- and trichloroethylene-dechlorinating consortium. Adhesion of these organisms was evaluated by microscopic determination of the numbers of cells that attached to glass coverslips exposed to cell suspensions under anaerobic conditions. We studied the effects of the growth phase of the organisms on adhesion, as well as the influence of electrostatic and hydrophobic properties of the substratum. Results indicate that S. wolfei adheres in considerably higher numbers to glass surfaces than the other three organisms. Starvation greatly decreases adhesion of S. wolfei and Desulfovibrio sp. strain G11 but seems to have less of an effect on the adhesion of the other bacteria. The presence of Fe³⁺ on the substratum, which would be electropositive, significantly increased the adhesion of S. wolfei, whereas the presence of silicon hydrophobic groups decreased the numbers of attached cells of all species. Measurements of transport of cells through hydrophobic-interaction and electrostatic-interaction columns indicated that all four species had negatively charged cell surfaces and that D. tiedjei and Desulfovibrio sp. strain G11 possessed some hydrophobic cell surface properties. These findings are an early step toward understanding the dynamic attachment of anaerobic bacteria in anoxic environments.     

Differential Effects of Oxygen and Oxidation Reduction Potential on the Multiplication of Three Species of Anaerobic Intestinal Bacteria

The sensitivity of three strains of anaerobic intestinal bacteria, Clostridium perfringens, Bacteroides fragilis, and Peptococcus magnus, to the differential effects of oxygen and adverse oxidation-reduction potential was measured. The multiplication of the three organisms was inhibited in the presence of oxygen whether the medium was at a negative oxidation-reduction potential (Eh of -50 mV), poised by the intermittent addition of dithiothreitol, or at a positive oxidation-reduction potential (Eh of near +500 mV). However, when these organisms were cultured in the presence of oxygen, no inhibition was observed, even when the oxidation-reduction potential was maintained at an average Eh of +325 mV by the addition of potassium ferricyanide. When the cultures were aerated, the growth patterns of the three organisms demonstrated different sensitivities to oxygen. P. magnus was found to be the most sensitive. After 2 h of aerobic incubation, no viable organisms could be detected. B. fragilis was intermediately sensitive to oxygen with no viable organisms detected after 5 h of aerobic incubation. C. perfringens was the least sensitive. Under conditions of aerobic incubation, viable organisms survived for 10 h. During the experiments with Clostridium, no spores were observed by spore staining.     

Antibiotic Production by Anaerobic Bacteria

Soils from aerobic and anaerobic sources were investigated for the possible presence of bacteria which produce antibiotics under anaerobic conditions of growth. The screening techniques devised for this study yielded 157 soil bacteria which, during anaerobic growth, produced antibiotic activity against aerobic test bacteria.

Studies on choice of media, presence of oxygen, and changes in antibiotic activity during growth indicated that representative strains of these bacteria produced mixtures of antibiotics. The activity was heat labile.

     

Ethanol Tolerance in Bacteria

Abstract

One promising application of biotechnology is in making the production of energy and chemical products from plants (“biomass”) practical. Applications include new markets for crops and reduction of wastes by using field residues or “wastelands” as feedstocks in biomass energy production. In addition, engineered crops could synthesize complex compounds. However, conversion to widespread use of biomass could have undesirable impacts. For example, changes in cropping practices may reduce wildlife populations or disrupt food chains. Other negative impacts of an environmentally insensitive development might include increased release of CO₂ (worsening global warming), and production of wastes, either water, chemical or biological, that present disposal problems. Biotechnology applied to biomass and chemical production has the potential for aiding economic development while greatly improving environmental quality. Environmental concerns are expressed in this paper, in the belief that consideration of potential problems at the inception of a technology increases the likelihood that environmentally sound courses will be pursued.     

厌氧细菌L型的诱导

用苯唑青霉素、羧苄青霉素对脆弱类杆菌、多形类杆菌、核梭杆菌、产气荚膜杆菌和艰难杆菌等5种厌氧菌进行L型菌的诱导。通过诱导,可见到脆弱类杆菌、多形类杆菌和产气荚膜杆菌形成油煎蛋状或颗粒状菌落。革兰氏染色镜检,见到菌体肿胀,并有丝状体、圆球体和巨球体。细胞壁染色法可见到部分细菌因胞壁缺损而被结晶紫透入菌体着色。诱导后的少数细菌可转变成可滤过型而能通过0.4μm孔径的滤膜。核梭杆菌诱导后形态改变极显著而较难识别。艰难杆菌形态改变小。建设在临床标本细菌培养时,有时尚需增加L型厌氧菌培养,以提高检出率。     

玉米耐铝毒基因的分离

以抑制消减杂交（SSH）为手段,以玉米对铝敏感的自交系Mo17和耐铝的自交系TL94B为材料,分别构建它们的正向和反向消减文库,分别筛选获得了124、47、103和64个阳性克隆。对文库的鉴定表明,插入片段分布在0.25-1．0kb之间,阳性克隆率在18％左右。对338个阳性克隆进行测序,得到232种表达序列标签（EST）,其中70．2％的EST可推测其功能。结果表明,玉米的铝离子胁迫反应涉及胁迫因子的信号传导、响应基因的转录表达与调控、物质的合成与运输、细胞结构和功能的改变等。     

Antibiotic Susceptibility of Anaerobic Ruminal Bacteria

This study demonstrated that 15 species of ruminal bacteria with no previous history of contact with antibiotics are susceptible to bacitracin, chloramphenicol, chlortetracycline, erythromycin, novobiocin, oleandomycin, oxytetracycline, penicillin, tetracycline, tylosin, and vancomycin. A number of the species were not inhibited by kanamycin, neomycin, polymyxin, and streptomycin. The data suggest that antibiotic-resistant cells occur within susceptible cultures of these species. Streptococcus bovis FD-10 and a nonruminal anaerobe, Bacteroides melaninogenicus BE-1, showed similar antibiotic susceptibilities.