Characterization and functional expression of a rubber degradation gene of a Nocardia degrader from a rubber-processing factory.

A rubber-degrading bacterial consortium named H2DA was obtained from an enrichment culture with natural rubber latex and rubber-processing factory waste in Vietnam. Gel permeation chromatography analysis revealed that only the strain NVL3 degraded synthetic poly(cis-1,4-isoprene) into low-molecular-weight intermediates among the three strains found in the H2DA. The 16S-rRNA gene sequence of NVL3 showed the highest identity with that of Nocardia farcinica DSM 43665T. NVL3 accumulated aldehyde intermediates from synthetic poly(cis-1,4-isoprene) on a rubber-overlay plate as indicated by Schiff's staining. NVL3 also degraded deproteinized natural rubber into low-molecular-weight aldehyde intermediates. A latex-clearing protein (lcp) gene ortholog was identified within the genome sequence of NVL3, and it showed a moderate amino-acid identity (54-75%) with the lcp genes from previously reported rubber degraders. The heterologous expression of the NVL3 lcp in Escherichia coli BL21(DE3) allowed us to purify the 46.8-kDa His-tagged lcp gene product (His-Lcp). His-Lcp degraded synthetic poly(cis-1,4-isoprene) and accumulated aldehyde intermediates from deproteinized natural rubber suggesting the functional expression of the lcp gene from a Nocardia degrader in E. coli. Quantitative reverse transcription PCR analysis indicated the strong transcriptional induction of the lcp gene in NVL3 in the presence of synthetic poly(cis-1,4-isoprene). These results suggest the involvement of the lcp gene in rubber degradation in NVL3.

Flow cytometry-based method for isolating live bacteria with meta-cleavage activity on dihydroxy compounds of biphenyl.

A new method for isolating targeted live bacterial cells was established with the use of cell sorting by flow cytometry (FCM) based on the fluorescence of the intermediate metabolite of biphenyl degradation. During biphenyl degradation, a PCB degrader, Comamonas testosteroni TK102, produces a meta-cleavage intermediate metabolite, 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA), which emits green fluorescence. HOPDA was produced from 2,3-dihydroxy biphenyl as a substrate, but it was not appropriate for labeling cells because it was released from the cells into the medium. When we used 4-n-butylbiphenyl and 4-n-heptylbiphenyl, we found that the cells produced and accumulated 2,3-dihydroxy intermediate metabolites. By the addition of synthesized 2,3-dihydroxy-4'-butylbiphenyl (2,3-DHBBP), we were able to label the cells with strong green fluorescence, suggesting the persistence of fluorescent intermediate metabolite in the cells by the introduction of the alkyl tail. 2,3-DHBBP was then used to label strain TK102 and the cells were sorted with FCM. The sorting efficiency of FCM was defined as the percentage of colony numbers per sorting events. Strain TK102 cells were successfully enriched by 4.1-fold from the mixture with environmental indigenous bacteria with a sorting efficiency of 7.3%. The method we present here serves as a basic technique for the specific and direct isolation of live bacterial cells which contain dioxygenases active on dihydroxylated aromatic compounds.