Changes in the size and composition of intracellular pools of nonesterified coenzyme A and coenzyme A thioesters in aerobic and facultatively anaerobic bacteria.

Intracellular levels of three coenzyme A (CoA) molecular species, i.e., nonesterified CoA (CoASH), acetyl-CoA, and malonyl-CoA, in a variety of aerobic and facultatively anaerobic bacteria were analyzed by the acyl-CoA cycling method developed by us. It was demonstrated that there was an intrinsic difference between aerobes and facultative anaerobes in the changes in the size and composition of CoA pools. The CoA pools in the aerobic bacteria hardly changed and were significantly smaller than those of the facultatively anaerobic bacteria. On the other hand, in the facultatively anaerobic bacteria, the size and composition of the CoA pool drastically changed within minutes in response to the carbon and energy source provided. Acetyl-CoA was the major component of the CoA pool in the facultative anaerobes grown on sufficient glucose, although CoASH was dominant in the aerobes. Therefore, the acetyl-CoA/CoASH ratios in facultatively anaerobic bacteria were 10 times higher than those in aerobic bacteria. In Escherichia coli K-12 cells, the addition of reagents to inhibit the respiratory system led to a rapid decrease in the amount of acetyl-CoA with a concomitant increase in the amount of CoASH, whereas the addition of cerulenin, a specific inhibitor of fatty acid synthase, triggered the intracellular accumulation of malonyl-CoA. The acylation and deacylation of the three CoA molecular species coordinated with the energy-yielding systems and the restriction of the fatty acid-synthesizing system of cells. These data suggest that neither the accumulation of acetyl-CoA nor that of malonyl-CoA exerts negative feedback on pyruvate dehydrogenase and acetyl-CoA carboxylase, respectively.     

Aerobic and facultatively anaerobic cellulolytic bacteria from the gut of the termite Zootermopsis angusticollis

AIMS: To demonstrate the occurrence of cellulolytic bacteria in the termite Zootermopsis angusticollis. METHODS AND RESULTS: Applying aerobic cultivation conditions we isolated 119 cellulolytic strains from the gut of Z. angusticollis, which were assigned to 23 groups of aerobic, facultatively anaerobic or microaerophilic cellulolytic bacteria. 16S rDNA restriction fragment pattern and partial 16S rDNA sequence analysis, as well as numerical taxonomy, were used for the assignment of the isolates. The Gram-positive bacteria of the actinomycetes branch could be assigned to the order Actinomycetales including the genera Cellulomonas/Oerskovia, Microbacterium and Kocuria. The Gram-positive bacteria from the order Bacillales belonged to the genera Bacillus, Brevibacillus and Paenibacillus. Isolates related to the genera Afipia, Agrobacterium/Rhizobium, Brucella/Ochrobactrum, Pseudomonas and Sphingomonas/Zymomonas from the alpha-proteobacteria and Spirosoma-like from the "Flexibacteriaceae" represented the Gram-negative bacteria. CONCLUSIONS: A cell titre of up to 10(7) cellulolytic bacteria per ml, determined for some isolates, indicated that they may play a role in cellulose digestion in the termite gut in addition to the cellulolytic flagellates and termite's own cellulases. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of bacteria on cellulose degradation in the termite gut has always been a matter of debate. In the present survey we investigated the aerobic and facultatively anaerobic cellulolytic bacteria in the termite gut.     

Mesophilic aerobic Gram negative cellulose degrading bacteria from aquatic habitats and soils

New procedures have been developed for the isolation and purification of aerobic and facultatively anaerobic bacteria able to utilize cellulose as sole source of carbon and energy. Wood pulp medium was used for enrichment, and bacterial cellulose, obtained from cultures of Acetobacter aceti subsp. xylinus , was employed as carbon substrate during purification and for the rapid screening of colonies for cellulolytic activity. The methods have revealed several new groups of Gram negative cellulose-degrading bacteria, including organisms that form differentiated colonies superficially similar to myxobacterial sori. The organisms formed several phenetic clusters, three of which contained reference strains of Cellvibrio fulvus, Pseudomonas fluorescens var. cellulosa and Cytophaga hutchinsonii . No cellulose degrading cluster included non-cellulose degrading strains. Most of the cellulose degraders studied were flagellated and, of these, the majority had polar or lophotrichous flagella, although one cluster included peritrichously flagellated organisms. The cellulose degraders in this study included five organisms that grew on nitrate-free medium; these appeared in two different clusters. A few Gram positive isolates appeared to belong to the genera Streptomyces and Thermoactinomyces .     

儿童乳牙根管感染的细菌学分析

对18例3～8岁儿童乳牙的根管感染以无菌技术进行定量取样,按种于12种选择性培养基和2种非选择性培养基上,进行需氧、微需氧和厌氧培养,并对细菌菌落计数。对牙髓拟杆菌和牙龈拟杆菌作半定量免疫荧光染色计数;并对其中9例病牙进行了菌相分析。检出的所有细菌中,厌氧菌占绝对优势;其中检出率较高的菌为:产黑色素拟杆菌属,厌氧革兰氏阳性球菌,微需氧革兰氏阳性球菌等.本试验证明,儿童乳牙根管感染是以厌氧菌为主的混合感染,其中以产黑色素拟杆菌属等最常见.     

Degradation of anaerobic reductive dechlorinationproducts of Aroclor 1242 by four aerobic bacteria

We studied the aerobic degradation of eight PCB congeners which comprise from 70 to 85% of the anaerobic dechlorination products from Aroclor 1242, including2-, 4-, 2,4-, 2,6-, 2,2'-, 2,4'-, 2,2',4-, and2,4,4'-chlorobiphenyl (CB), and the biodegradation of their mixtures designed to simulate anaerobic dechlorination profiles M and C. StrainsComamonas testosteroni VP44 and Rhodococcus erythreus NY05 preferentially oxidizeda para-substituted ring, while Rhodococcus sp. RHA1, similar to well known strain Burkholderia sp. LB400, preferably attackedan ortho-chlorinated ring. Strains with ortho-directed attack extensively degraded2,4'- and 2,4,4'-CB into 4-chlorobenzoate, while bacteria with para-directed attack transformed these congeners mostly into potentially problematicmeta-cleavage products. The strains that preferentiallyoxidized an ortho-substituted ring readily degradedseven of the eight congeners supplied individually; only 2,6-CB was poorly degraded. Degradationof 2,2'- and 2,4,4'-CB was reduced when present in mixtures M and C. Higher efficiencies of degradation of the individual congeners and defined PCB mixtures M and C and greater production of chlorobenzoates were observed with bacteria that preferentially attackan ortho-substituted ring. PCB congeners 2,4'-, 2,2',4-, and 2,4,4'-CB canbe used to easily identify bacteria with ortho-directed attack whichare advantageous for use in the aerobic stage of the two-phase (anaerobic/aerobic)PCB bioremediation scheme.     

Diversity and dynamics of bacterial species in a biofilm at the end of the Seoul water distribution system

To investigate changes in the bacterial species and hygienic safety of the biofilm at the end of the drinking water distribution system in Seoul (Korea), denaturing gradient gel electrophoresis (DGGE) and DNA sequencing were used to analyse the bacterial population in the biofilm of a semi-pilot galvanized iron pipe model. The presence of sequences from aerobic Sphingomonas sp., anaerobic Rhodobacter sp., and unculturable bacteria indicated that these organisms coexisted after 1 day of model operation, demonstrating the ease of biofilm formation on galvanized iron pipes in the end region of the water distribution system studied. Sequences similar to those of unculturable bacteria, E. coli, and anaerobic bacteria were detected during the course of succession on the biofilm. More complicated band patterns were observed after 70 days of operation. PCR-DGGE illustrated changes in the biofilm during succession as well as the possibilities of anaerobic conditions and faecal contamination of the drinking water system. PCR-DGGE and culture-dependent fatty acid methyl ester (FAME) analysis showed different patterns for the same samples (Lee & Kim 2003); however, PCR-DGGE showed less diversity than did FAME analysis. This study compared the culture-dependent FAME and culture-independent PCR-DGGE methods directly, and their use in promoting the hygienic safety of drinking water.     

Hydrogen peroxide-forming NADH oxidase belonging to the peroxiredoxin oxidoreductase family: existence and physiological role in bacteria

Amphibacillus xylanus and Sporolactobacillus inulinus NADH oxidases belonging to the peroxiredoxin oxidoreductase family show extremely high peroxide reductase activity for hydrogen peroxide and alkyl hydroperoxides in the presence of the small disulfide redox protein, AhpC (peroxiredoxin). In order to investigate the distribution of this enzyme system in bacteria, 15 bacterial strains were selected from typical aerobic, facultatively anaerobic, and anaerobic bacteria. AhpC-linked alkyl hydroperoxide reductase activities were detected in most of the tested strains, and especially high activities were shown in six bacterial species that grow well under aerobic conditions, including aerobic bacteria (Alcaligenes faecalis and Bacillus licheniformis) and facultatively anaerobic bacteria (Amphibacillus xylanus, Sporolactobacillus inulinus, Escherichia coli, and Salmonella enterica serovar Typhimurium). In the absence of AhpC, the purified enzymes from A. xylanus and S. inulinus catalyze the NADH-linked reduction of oxygen to hydrogen peroxide. Similar activities were observed in the cell extracts from each of these six strains. The cell extract of B. licheniformis revealed the highest AhpC-linked alkyl hydroperoxide reductase activity in the four strains, with V(max) values for hydrogen peroxide and alkyl hydroperoxides being similar to those for the enzymes from A. xylanus and S. inulinus. Southern blot analysis of the three strains probed with the A. xylanus peroxiredoxin reductase gene revealed single strong bands, which are presumably derived from the individual peroxiredoxin reductase genes. Single bands were also revealed in other strains which show high AhpC-linked reductase activities, suggesting that the NADH oxidases belonging to the peroxiredoxin oxidoreductase family are widely distributed and possibly play an important role both in the peroxide-scavenging systems and in an effective regeneration system for NAD in aerobically growing bacteria.     

Nitrate-dependent anaerobic carbon monoxide oxidation by aerobic CO-oxidizing bacteria

Two dissimilatory nitrate-reducing (Burkholderia xenovorans LB400 and Xanthobacter sp. str. COX) and two denitrifying isolates (Stappia aggregata IAM 12614 and Bradyrhizobium sp. str. CPP), previously characterized as aerobic CO oxidizers, consumed CO at ecologically relevant levels (<100 ppm) under anaerobic conditions in the presence, but not absence, of nitrate. None of the isolates were able to grow anaerobically with CO as a carbon or energy source, however, and nitrate-dependent anaerobic CO oxidation was inhibited by headspace concentrations >100-1000 ppm. Surface soils collected from temperate, subtropical and tropical forests also oxidized CO under anaerobic conditions with no lag. The observed activity was 25-60% less than aerobic CO oxidation rates, and did not appear to depend on nitrate. Chloroform inhibited anaerobic but not aerobic activity, which suggested that acetogenic bacteria may have played a significant role in forest soil anaerobic CO uptake.     

Enhanced biodegradation of aromatic pollutants in cocultures of anaerobic and aerobic bacterial consortia

Toxic aromatic pollutants, concentrated in industrial wastes and contaminated sites, can potentially be eliminated by low cost bioremediation systems. Most commonly, the goal of these treatment systems is directed at providing optimum environmental conditions for the mineralization of the pollutants by naturally occurring microflora. Electrophilic aromatic pollutants with multiple chloro, nitro and azo groups have proven to be persistent to biodegradation by aerobic bacteria. These compounds are readily reduced by anaerobic consortia to lower chlorinated aromatics or aromatic amines but are not mineralized further. The reduction increases the susceptibility of the aromatic molecule for oxygenolytic attack. Sequencing anaerobic and aerobic biotreatment steps provide enhanced mineralization of many electrophilic aromatic pollutants. The combined activity of anaerobic and aerobic bacteria can also be obtained in a single treatment step if the bacteria are immobilized in particulate matrices (e.g. biofilm, soil aggregate, etc.). Due to the rapid uptake of oxygen by aerobes and facultative bacteria compared to the slow diffusion of oxygen, oxygen penetration into active biofilms seldom exceeds several hundred micrometers. The anaerobic microniches established inside the biofilms can be applied to the reduction of electron withdrawing functional groups in order to prepare recalcitrant aromatic compounds for further mineralization in the aerobic outer layer of the biofilm.Aside from mineralization, polyhydroxylated and chlorinated phenols as well as nitroaromatics and aromatic amines are susceptible to polymerization in aerobic environments. Consequently, an alternative approach for bioremediation systems can be directed towards incorporating these aromatic pollutants into detoxified humic-like substances. The activation of aromatic pollutants for polymerization can potentially be encouraged by an anaerobic pretreatment step prior to oxidation. Anaerobic bacteria can modify aromatic pollutants by demethylating methoxy groups and reducing nitro groups. The resulting phenols and aromatic amines are readily polymerized in a subsequent aerobic step.     

需氧菌阴道炎、细菌性阴道病阴道菌群分析

用阴道分泌物直接涂片、革兰染色、选择性培养分离和细菌预成酶谱分析等微生物学方法和生物化学方法,分析了正常女性、AV、BV患者的阴道菌群。正常女性阴道中以乳酸杆菌为主,产H2O2乳酸杆菌的检出率89%,AV的致病菌主要是革兰阳性率需氧菌、检出率可达80%,其中金黄色葡萄球菌,粪肠球菌和埃希氏大肠菌较为常见,B族链球菌的检出率较低;BV的致病菌主要是厌氧菌,以革兰阴性厌氧菌的检出率最高,加德纳菌的检出率不足40%。48例BV患者中有8例合并AV感染,31例AV患者中有6例合并BV感染。细菌谱分析发现,AV患者易感染消化链球菌、普雷沃菌等厌氧菌和加德纳菌,BV患者易感染粪肠球菌、大肠埃希菌等需氧菌。     

Effects of larval mosquitoes (Aedes triseriatus) and stemflow on microbial community dynamics in container habitats.

The dynamics of the microbial food sources for Aedes triseriatus larvae in microcosms were found to be strongly influenced by larval presence. The total abundance of bacteria in water samples generally increased in response to larvae, including populations of cultivable, facultatively anaerobic bacteria. Additionally, a portion of the community shifted from Pseudomonaceae to Enterobacteriaceae. Bacterial abundance on leaf material was significantly reduced in the presence of actively feeding larvae. Principle-component analysis of whole community fatty acid methyl ester (FAME) profiles showed that larvae changed the microbial community structure in both the water column and the leaf material. Cyclopropyl FAMEs, typically associated with bacteria, were reduced in microcosms containing larvae; however, other bacterial fatty acids showed no consistent response. Long-chain polyunsaturated fatty acids characteristic of microeukaryotes (protozoans and meiofauna) declined in abundance when larvae were present, indicating that larval feeding reduced the densities of these microorganisms. However, presumed fungal lipid markers either increased or were unchanged in response to larvae. Larval presence also affected microbial nitrogen metabolism through modification of the physiochemical conditions or by grazing on populations of bacteria involved in nitrification-denitrification. Stemflow primarily influenced inorganic ion and organic compound concentrations in the microcosms and had less-pronounced effects on microbial community parameters than did larval presence. Stemflow treatments diluted concentrations of all inorganic ions (chloride, sulfate, and ammonium) and organic compounds (total dissolved organic carbon, soluble carbohydrates, and total protein) measured, with the exceptions of nitrite and nitrate. Stemflow addition did not measurably affect larval biomass in the microcosms but did enhance development rates and early emergence patterns of adults.     

Bacterial translocation from the gastrointestinal tracts of thymectomized mice

The incidence of translocation of viable indigenous bacteria from the gastrointestinal tract to the mesenteric lymph node, spleen, liver, and kidney was compared in neonatally thymectomized mice and sham-thymectomized specific pathogen-free mice. The immunologic responses of the thymectomized mice to sheep erythrocytes were decreased compared to the responses of sham-thymectomized mice. Strictly anaerobic bacteria were isolated from only 1.8% of the organs from thymectomized mice and from none of the organs of shamthymectomized mice. Aerobic or facultatively anaerobic bacteria were cultured from 27.4% of the organs of thymectomized mice. Of the thymectomized mice, 70.7% contained viable aerobic or facultatively anaerobic bacteria in one or more of their organs tested, compared with only 10% of the sham-thymectomized mice.Escherichia coli was the predominant bacterial species isolated from these organs, althoughStaphylococcus aureus, Streptococcus, andCorynebacterium also were present.Bacteroides were the only strictly anaerobic bacteria cultured. Neonatal thymectomy promotes the translocation of certain indigenous bacteria from the gastrointestinal tract to the mesenteric lymph node, spleen, liver, and kidney.     

The aerobic and anaerobic microbiology of pustular acne lesions

Specimens from 32 pustular acne lesions that were inoculated on media supportive for the growth of aerobic and anaerobic bacteria showed bacterial growth. Only aerobic or facultative bacteria were recovered in 15 (47%) specimens, only anaerobic bacteria in 11 (34%) specimens, and mixed aerobic and anaerobic bacteria in 6 (18%) specimens. A total of 57 isolates, 31 anaerobes (1.0 per specimen) and 26 aerobes (0.8 per specimen) were recovered. The predominant isolates were Staphylococcus sp. (19 isolates), Peptostreptococcus sp. (15), and Propionibacterium sp. (10). Twelve (37.5%) of the comedones yielded only one organism. This retrospective study highlighted the polymicrobial nature of over two-thirds of culture positive pustular acne lesions and suggests the potential for pathogenic role of aerobic and anaerobic organisms other than P. acnes and Staphylococcus sp. in acne vulgaris.     

Microbial growth on carbon monoxide

The utilization of carbon monoxide as energy and/or carbon source by different physiological groups of bacteria is described and compared. Utilitarian CO oxidation which is coupled to the generation of energy for growth is achieved by aerobic and anaerobic eu- and archaebacteria. They belong to the physiological groups of aerobic carboxidotrophic, facultatively anaerobic phototrophic, and anaerobic acetogenic, methanogenic or sulfate-reducing bacteria. The key enzyme in CO oxidation is CO dehydrogenase which is a molybdo iron-sulfur flavoprotein in aerobic CO-oxidizing bacteria and a nickel-containing iron-sulfur protein in anaerobic ones. In carboxidotrophic and phototrophic bacteria, the CO-born CO₂ is fixed by ribulose bisphosphate carboxylase in the reductive pentose phosphate cycle. In acetogenic, methanogenic, and probably in sulfate-reducing bacteria, CODH/acetyl-CoA synthase directly incorporates CO into acetyl-CoA.In plasmid-harbouring carboxidotrophic bacteria, CO dehydrogenase as well as enzymes involved in CO₂ fixation or hydrogen utilization are plasmid-encoded. Structural genes encoding CO dehydrogenase were cloned from carboxidotrophic, acetogenic and methanogenic bacteria. Although they are clustered in each case, they are genetically distinct.Soil is a most important biological sink for CO in nature. While the physiological microbial groups capable of CO oxidation are well known, the type and nature of the microorganisms actually representing this sink are still enigmatic. We also tried to summarize the little information available on the nutritional and physicochemical requirements determining the sink strength. Because CO is highly toxic to respiring organisms even in low concentrations, the function of microbial activities in the global CO cycle is critical.     

Distribution of ubiquinones (coenzyme Q) in Gram negative bacillae]

The coenzyme Q system was examined on 55 strains of Gram negative aerobic or facultatively anaerobic rods. No bacteria contain Co-Q7 nor Co-Q10. Ubiquinone Q8 predominates in Flavobacterium and in Enterobacteriaceae; Q9 was the only homolog found in the Pseudomonas, and predominates in the Acinetobacter.     

Nitrogen Fixation in Seawater

S ummary . The acetylene reduction technique was used for a 3-year period to monitor potential nitrogen fixation by aerobic heterotrophic bacteria in the sea 2 miles offshore in Cardigan Bay. Samples from depths down to 15 m were membrane-filtered and the residues incubated aerobically or anaerobically in acetylene-containing gas mixtures in sealed Millipore Field Monitors. Pure cultures of aerobic heterotrophs isolated from spread-plates or monitor membranes supplied with 'nitrogen-free'media, were tested for ability to reduce acetylene. Glucose was the best of 14 substrates tested to support both growth and acetylene reduction by marine bacteria. The results suggested the presence of a few aerobic or facultatively anaerobic nitrogen fixers among much more numerous and efficient 'fixed-nitrogen-scavengers'. The acetylene-reducing capacity of pure cultures was inexplicably variable, even under closely-standardized conditions: this is discussed. The more consistent acetylene reducers included various-sized rods (Gram positive and negative), coccobacilli and yeasts, which latter may have had non-culturable bacteria associated with them. No recognizable Azotobacter sp. was isolated, despite the strongly-selective conditions imposed. Similar results were obtained for seawater samples from the Irish Sea and an Iceland fjord.     

Diazotrophs in the digestive tract of termite Neotermes castaneus

Normal vital activity of termites Neotermes castaneus requires the presence and continuous replenishment of transient nitrogen-fixing bacteria in their digestive tract, which is realized by coprophagy and repeated utilization of substrate enriched in termite feces. This is the first demonstration of significant changes in the complex of aerobic and facultatively anaerobic nitrogen fixers mediated by an extension of microbial group composition and a shift in dominant taxa in termites that cannot reutilize their feces.     

Anaerobic and aerobic degradation of pyridine by a newly isolated denitrifying bacterium.

New denitrifying bacteria that could degrade pyridine under both aerobic and anaerobic conditions were isolated from industrial wastewater. The successful enrichment and isolation of these strains required selenite as a trace element. These isolates appeared to be closely related to Azoarcus species according to the results of 16S rRNA sequence analysis. An isolated strain, pF6, metabolized pyridine through the same pathway under both aerobic and anaerobic conditions. Since pyridine induced NAD-linked glutarate-dialdehyde dehydrogenase and isocitratase activities, it is likely that the mechanism of pyridine degradation in strain pF6 involves N-C-2 ring cleavage. Strain pF6 could degrade pyridine in the presence of nitrate, nitrite, and nitrous oxide as electron acceptors. In a batch culture with 6 mM nitrate, degradation of pyridine and denitrification were not sensitively affected by the redox potential, which gradually decreased from 150 to -200 mV. In a batch culture with the nitrate concentration higher than 6 mM, nitrite transiently accumulated during denitrification significantly inhibited cell growth and pyridine degradation. Growth yield on pyridine decreased slightly under denitrifying conditions from that under aerobic conditions. Furthermore, when the pyridine concentration used was above 12 mM, the specific growth rate under denitrifying conditions was higher than that under aerobic conditions. Considering these characteristics, a newly isolated denitrifying bacterium, strain pF6, has advantages over strictly aerobic bacteria in field applications.     

Occurrence of hopanoid lipids in anaerobic Geobacter species

Geobacter metallireducens and G. sulfurreducens have been classified as strictly anaerobic bacteria which grow and thrive in subsurface and sediment environments. Hopanoids are pentacyclic triterpenoid lipids and are important for bacterial membrane stability and functioning. Hopanoids predominantly occur in aerobically growing bacteria of oxic environments. They rarely have been found in facultatively anaerobic bacteria and, to date, not at all in strict anaerobes. Our research shows that anaerobically grown G. metallireducens and G. sulfurreducens bacteria contain a range of hopanoid lipids, such as diploptene (i.e. hop-22(29)-ene) and hop-21-ene, and more complex, elongated hopanoids. In geological formations, diagenetic derivatives of hopanoids are widely used as biomarkers and are recognized as molecular fossils of bacterial origin. To date, these biomarkers have largely been interpreted as those derived from ancient oxic environments. Our findings presented here suggest that this interpretation needs to be re-evaluated. In addition to the origin in oxic environments, 'geohopanoids' may originate from ancient anaerobic environments as well.