Identification and Genetic Characterization of Phenol-Degrading Bacteria from Leaf Microbial Communities

Abstract

Microbial communities on aerial plant leaves may contribute to the degradation of organic air pollutants such as phenol. Epiphytic bacteria capable of phenol degradation were isolated from the leaves of green ash trees grown at a site rich in airborne pollutants. Bacteria from these communities were subjected, in parallel, to serial enrichments with increasing concentrations of phenol and to direct plating followed by a colony autoradiography screen in the presence of radiolabeled phenol. Ten isolates capable of phenol mineralization were identified. Based on 16S rDNA sequence analysis, these isolates included members of the genera Acinetobacter, Alcaligenes, and Rhodococcus. The sequences of the genes encoding the large subunit of a multicomponent phenol hydroxylase (mPH) in these isolates indicated that the mPHs of the gram-negative isolates belonged to a single kinetic class, and that is one with a moderate affinity for phenol; this affinity was consistent with the predicted phenol levels in the phyllosphere. PCR amplification of genes for catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) in combination with a functional assay for C23O activity provided evidence that the gram-negative strains had the C12O-, but not the C23O-, phenol catabolic pathway. Similarly, the Rhodococcus isolates lacked C23O activity, although consensus primers to the C12O and C23O genes of Rhodococcus could not be identified. Collectively, these results demonstrate that these leaf surface communities contained several taxonomically distinct phenol-degrading bacteria that exhibited diversity in their mPH genes but little diversity in the catabolic pathways they employ for phenol degradation.

Bacterial biosynthesis of 1-aminocyclopropane-1-caboxylate (ACC) deaminase, a useful trait to elongation and endophytic colonization of the roots of rice under constant flooded conditions

“…Genomic DNA was isolated according to Sandhu et al (2009). The amplification of 16S rDNA gene was done by using universal bacterial primer 1492R (50-TAC GGY TACCTT GTT ACG ACT T-30) and 27F (50-AGA GTT TGATCM TGG CTC AG-30) in accordance with the conditions described by Sandhu et al (2009).…”

Degradation of pyridine by one Rhodococcus strain in the presence of chromium (VI) or phenol

“…The phenol hydroxylase gene of strain Chr-9 was amplified and sequenced using the following primer sets, PheU-f (CGKATGACSTACGGCTGGATGGGCG) and PheU-r (ACGTCCTGTTC-GATGATCTCCTTGATCCGC), according to a previously described protocol [33]. The gene sequence has been deposited in GenBank under accession No.…”

“…T-5 and T-10 (GenBank accession No. FJ392542 and FJ392543) [33]. Therefore, strain Chr-9 was designated as Rhodococcus sp.…”

Isolation and Genetic Characterization of Aurantimonas and Methylobacterium Strains from Stems of Hypernodulated Soybeans

“…(Table S3). Members of these genera have been isolated from the phyllosphere and are reported to be degraders of air pollutants (44,60) and to be methylotrophic (4,27), suggesting that they might also play a role as scavengers of monocarbon wastes from plants similar to the role played by Methylobacterium species in the phyllosphere (6).…”