Complex microbial communities from river biofilms might contain microorganisms capable of degrading xenobiotic pollutants such as pesticides (e.g. methomyl, which is commonly detected in rivers). Therefore, this study was used to determine the methomyl degradation potential of bacteria consortia and single bacterial strains acclimatized and isolated from natural river biofilms to provide biomaterials for bioremediation of water that is contaminated with methomyl. Natural river biofilms were culture enriched with methomyl as the sole carbon source to obtain acclimatized bacterial consortia and single bacterial strains. The microbial consortium on the ceramic discs was able to remove 91 % of added methomyl (50 mg l -1 ) in 7 days. The longer-acclimatized bacterial consortium on loofah sponges removed methomyl more quickly than the shorter-acclimatized consortium, but both had similar removal capabilities (i.e. 92.4 and 92.2 %). This finding suggested that the former might contain more methomyl degraders than the latter. However, after preservation at 25, 4 and -20°C for 1 or 3 months, the methomyl degradation ability of the bacterial consortia decreased significantly, indicating loss of methomyl degraders during preservation. Three bacterial species were isolated from acclimatized river biofilms, and only one species, identified as Sphingomonas sp., was able to remove methomyl, with a 7-day removal rate of 44.7 % when sugar was added and of 32.5 % when no sugar was added. These results suggested that an additional carbon source might slightly improve the ability of Sphingomonas sp. to degrade methomyl. Acclimatized bacterial consortia have a higher potential for treating methomyl-contaminated water than isolated bacterial species.
Abnormally high circulating androgen levels have been considered a causative factor for benign prostatic hypertrophy and prostate cancer in men. Recent animal studies on gut microbiome suggested that gut bacteria are involved in sex steroid metabolism; however, the underlying mechanisms and bacterial taxa remain elusive. Denitrifying betaproteobacteria
Thauera
spp. are metabolically versatile and often distributed in the animal gut.
Thauera
sp. strain GDN1 is an unusual betaproteobacterium capable of catabolizing androgen under both aerobic and anaerobic conditions. We administered C57BL/6 mice (aged 7 weeks) with strain GDN1 through oral gavage. The strain GDN1 administration caused a minor increase in the relative abundance of
Thauera
(≤0.1%); however, it has profound effects on the host physiology and gut bacterial community. The results of our ELISA assay and metabolite profile analysis indicated an approximately 50% reduction in serum androgen levels in the strain GDN1-administered male mice. Moreover, androgenic ring-cleaved metabolites were detected in the fecal extracts of the strain GDN1-administered mice. Furthermore, our RT – qPCR results revealed the expression of the androgen catabolism genes in the gut of the strain GDN1-administered mice. We found that the administered strain GDN1 regulated mouse serum androgen levels, possibly because it blocked androgen recycling through enterohepatic circulation. This study discovered that sex steroids serve as a carbon source of gut bacteria; moreover, host circulating androgen levels may be regulated by androgen-catabolizing gut bacteria. Our data thus indicate the possible applicability of androgen-catabolic gut bacteria as potent probiotics in alternative therapy of hyperandrogenism.
23 Steroid estrogens modulate physiology and development of vertebrates. Biosynthesis of C 18 24 estrogens from C 19 androgens by the O 2 -dependent aromatase is thought to be irreversible. Here, we 25 report a denitrifying Denitratisoma sp. strain DHT3 capable of catabolizing estrogens or androgens 26 anaerobically. Strain DHT3 genome contains a polycistronic gene cluster emtABCD differentially 27 transcribed under estrogen-fed conditions. emtABCD encodes a cobalamin-dependent 28 methyltransferase system conserved among estrogen-utilizing anaerobes; emtA-disrupted strain 29 DHT3 can catabolize androgens but not estrogens. These data, along with the observed androgen 30 production in estrogen-fed strain DHT3 cultures, indicate the occurrence of a cobalamin-mediated 31 estrogen methylation to form androgens. Consistently, the estrogen conversion into androgens in 32 strain DHT3 cell-extracts requires methylcobalamin and is inhibited by propyl-iodide, a specific 33 inhibitor of cobalamin-dependent enzymes. The identification of the cobalamin-mediated estrogen 34 methylation thus represents an unprecedented metabolic link between cobalamin and steroid 35 metabolism and suggests that retroconversion of estrogens into androgens occurs in the biosphere. 36 37
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