Kocuria rosea HN01, a newly alkaliphilic humus-reducing bacterium isolated from cassava dreg compost

The aims of this study were to isolate an alkaliphilic humus-reducing bacterium, investigate the fastest microbial reduction of humus analog as affected by different cultivation, and examine its ability for iron(III) oxide reduction and organochlorine pollutants (OCPs) degradation. A strain of pure culture, designated as HN01, was isolated from cassava dreg compost using anaerobic enrichment procedure with glucose as the electron donor and anthraquinone-2,6-disulphonate (AQDS) as the sole terminal electron acceptor. The isolate strain was identified using phenotypic and phylogenetic analysis. Iron(III) oxides and OCPs were chosen as potential electron acceptors. Strict anaerobic techniques and sterile conditions were applied throughout the incubation experiments, purged with O-2-free N-2 for 15 min. The concentration of reduced AQDS and Fe(II) was then quantified using a UV-vis spectrophotometer. The concentration of OCPs was analyzed by gas chromatography with a micro-electron capture detector. Cell number was determined by direct plate counting on aerobic Luria-Bertani medium agar medium at pH 9. (1) Strain HN01 was identified as Kocuria rosea, and the AQDS reduction by HN01 was observed in NaCl concentrations below 12 % (w/v) (optimum, 10 %) and pH ranges of 6.0-10.0 (optimum, 9.0) with sucrose as electron donor at 30 A degrees C; (2) glucose, sucrose, methanol, ethanol, glycerol, and acetate were the favorable electron donors for AQDS reduction by strain HN01; (3) the strain had the ability of reducing iron(III) oxides in the presence of sucrose at pH 9.0 and its Fe(III)-reducing capacity ranked as goethite (alpha-FeOOH) > lepidocrocite (gamma-FeOOH) > haematite(alpha-Fe2O3); and (4) the strain could effectively dechlorinate p,p'-DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane), and the dechlorination rate reached 71.3 %. This is the first report of a strain of K. rosea capable of reducing AQDS, iron (III) oxides, and p,p'-DDT, which extends the diversity of the alkaliphilic and halotolerant humus/Fe(III)-reducing bacterium associated with dechlorination. The strain may have the potential to be used for bioremediation of an anoxic alkaline wastewater or site contaminated with OCPs.