Benzene has often been observed to be resistant to microbial degradation under anoxic conditions. A number of recent studies, however, have demonstrated that anaerobic benzene utilization can occur. This study extends the previous reports of anaerobic benzene degradation to sediments that varied with respect to contamination input, predominant redox condition, and salinity. In spite of differences in methodology, microbial degradation of benzene was noted in slurries constructed with sediments from various geographical locations and range from aquifer sands to fine-grained estuarine muds, under methanogenic, sulfate-reducing, and iron-reducing conditions. In aquifer sediments under methanogenic conditions, benzene loss was concomitant with methane production, and microbial utilization of [14C]benzene yielded 14CO2 and 14CH4. In slurries with estuarine and aquifer sediments under sulfate-reducing conditions, the loss of sulfate in amounts consistent with the stoichiometric degradation of benzene or the conversion of [14C]benzene to 14CO2 indicates that benzene was mineralized. Benzene loss also occurred in the presence of Fe(III) in sediments from freshwater environments. Microbial benzene utilization, however, was not observed under denitrifying conditions. These results indicate that the potential for the anaerobic degradation of benzene, which was once thought to be resistant to non-oxygenase attack, exists in a variety of aquatic sediments from widely distributed locations.

A sulfate-reducing bacterial enrichment that anaerobically metabolized benzene was obtained from a petroleumcontaminated aquifer. During biodegradation, we observed the transient accumulation of phenol and benzoate as putative benzene intermediates. As these compounds are intermediates in many anaerobic metabolic pathways, we investigated their relation to anaerobic benzene decay with 13 C-labeled starting material. We were able to confirm the presence of [ 13 C]phenol and [ 13 C]benzoate as intermediates of anaerobic [ 13 C-UL]benzene decay. Mass spectral evidence indicated that the carboxyl group of benzoate also originated from 13 C-labeled benzene. Benzoate was also found as a putative benzene intermediate when inoculum from the same site was incubated under methanogenic conditions or when organisms enriched from a different petroleum-contaminated location were incubated with chelated Fe(III) as an electron acceptor. These findings are the first to confirm the importance of benzoate during anaerobic benzene metabolism and suggest that concerns over the accumulation of potentially recalcitrant intermediates in anaerobic environments contaminated with this substrate are unwarranted.

The ability of anaerobic microorganisms to degrade a wide variety of crude oil components was investigated using chronically hydrocarbon-contaminated marine sediments as the source of inoculum. When sulfate reduction was the predominant electron-accepting process, gas chromatographic analysis revealed almost complete n-alkane removal (C 15 -C 34 ) from a weathered oil within 201 d of incubation. No alteration of the oil was detected in sterile control incubations or when nitrate served as an alternate electron acceptor. The amount of sulfate reduced in the oilamended nonsterile incubations was more than enough to account for the complete mineralization of the n-alkane fraction of the oil; no loss of this anion was observed in sterile control incubations. The mineralization of the alkanes was confirmed using 14 C-14,15-octacosane (C 28 H 58 ), with 97% of the radioactivity recovered as 14 CO 2 . These findings extend the range of hydrocarbons known to be amenable to anaerobic biodegradation. Moreover, the rapid and extensive alteration in the n-alkanes can no longer be considered a defining characteristic of aerobic oil biodegradation processes alone.

bSince the first step of the infection process is colonization of the host, it is important to understand how Escherichia coli pathogens successfully colonize the intestine. We previously showed that enterohemorrhagic O157:H7 strain E. coli EDL933 colonizes a niche in the streptomycin-treated mouse intestine that is distinct from that of human commensal strains, which explains how E. coli EDL933 overcomes colonization resistance imparted by some, but not all, commensal E. coli strains. Here we sought to determine if other E. coli pathogens use a similar strategy. We found that uropathogenic E. coli CFT073 and enteropathogenic E. coli E2348/69 occupy intestinal niches that are distinct from that of E. coli EDL933. In contrast, two enterohemorrhagic strains, E. coli EDL933 and E. coli Sakai, occupy the same niche, suggesting that strategies to prevent colonization by a given pathotype should be effective against other strains of the same pathotype. However, we found that a combination of commensal E. coli strains that can prevent colonization by E. coli EDL933 did not prevent colonization by E. coli CFT073 or E. coli E2348/69. Our results indicate that development of probiotics to target multiple E. coli pathotypes will be problematic, as the factors that govern niche occupation and hence stable colonization vary significantly among strains.

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Alkalibaculum bacchi gen. nov., sp. nov., a CO-oxidizing, ethanol-producing acetogen isolated from livestock-impacted soil Phenotypic and phylogenetic studies were performed on three strains of an acetogenic bacterium isolated from livestock-impacted soil. The bacterium stained Gram-negative and was a nonspore-forming rod that was motile by peritrichous flagella. The novel strains had an optimum pH for growth of 8.0-8.5 and utilized H 2 : CO 2 , CO : CO 2 , glucose, fructose, mannose, turanose, ribose, trimethylamine, pyruvate, methanol, ethanol, n-propanol and n-butanol as growth substrates. Acetate was produced from glucose. Acetate, CO 2 and ethanol were produced from CO : CO 2 . 16S rRNA gene sequence analysis indicated that the novel strains formed a new subline in the family Eubacteriaceae (rRNA cluster XV) of the low G+C-containing Gram-positive bacteria of the class Clostridia. The DNA G+C base composition was 34 mol%. Cell wall analysis revealed the existence of a novel B-type peptidoglycan similar to the B2a-type (B4) configuration with a variation containing aspartic acid. Based on phylogenetic and phenotypic evidence, it is proposed that the new isolates represent a novel genus and species, for which the name Alkalibaculum bacchi gen. nov., sp. nov. is proposed. The type strain of the type species is CP11 T (5ATCC BAA-1772Biological ethanol (bioethanol) production has captured worldwide attention as a result of fluctuating oil prices as well as 'green' initiatives to displace petroleum and lower CO 2 emissions. Most bioethanol produced in the USA is derived from the fermentation of corn starch. The result of increasing bioethanol production is thus direct competition with a food commodity and so this source is not viewed as a long-term sustainable option (Pimentel, 2003). Cellulosic ethanol production is a desirable alternative but current technologies have not overcome the obstacles (e.g. pretreatment and waste disposal) associated with the direct fermentation of cellulosic material (Lynd et al., 2008). An alternative to direct fermentation is the indirect fermentation of lignocellulosic biomass to ethanol. Using this method, biomass (e.g. switchgrass, corn stover, etc.) is pyrolysed to produce synthesis gas (CO : CO 2 : H 2 ) (McKendry, 2002;van der Drift et al., 2001). Some acetogenic bacteria can convert the synthesis gas to ethanol through anaerobic fermentation (Datar et al., 2004). Phylogenetically, acetogens are a diverse group of organisms within the Gram-positive, low G+C Clostridia, of which representative micro-organisms are found in eight of 19 Clostridium clusters (I, V, VI, IX, XI, XII, XIVa and XV) (Collins et al., 1994;Drake et al., 2006).However, while indirect fermentation of biomass by acetogens is an attractive option for bioethanol production, relatively few micro-organisms are known that can convert synthesis gas to ethanol . Of the most promising acetogens to date, Clostridium ljungdahlii, Clostridium carboxidivorans and a micro-organism also isolated in our laboratory, Clostr...

Strain B66T was isolated from a marine water sample collected at Al Ruwais, located on the northern tip of Qatar. Cells were Gram-stain-negative, strictly aerobic and short- rod-shaped with a polar flagellum. The isolate was able to grow at 15–45 °C (optimum, 30 °C), at pH 5–11 (optimum, pH 6.5–8) and with 0–6 % NaCl. 16S rRNA gene sequence analysis revealed that strain B66T was affiliated with the family Alteromonadaceae , sharing the highest sequence similarities to the genera Alteromonas (93.7–95.4 %), Aestuariibacter (94.0–95.1 %), Agaribacter (93.3–93.7 %), Glaciecola (92.0–93.7 %), Marisendiminitalea (93.2–93.3 %) and Planctobacterium (92.9 %). In the phylogenetic trees, strain B66T demonstrated the novel organism formed a distinct lineage closely associated with Aestuariibacter and Planctobacterium . Major fatty acids were C16 : 0, summed feature 3 (C16 : 1  ω7c/C16 : 1  ω6c/iso-C15 : 0 2-OH and iso-C15 : 0 3-OH. The major respiratory quinone was ubiquinone-8 and the major polar lipids are phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content derived from the genome was 43.2 mol%. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic data, strain B66T is considered to represent a novel species and genus for which the name Ningiella ruwaisensis gen. nov., sp. nov., is proposed. The type strain is B66T (=QCC B003/17T=LMG 30288 T=CCUG 70703T).

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