Members Of Rhodococcus Research Articles

Time-resolved analysis of a denitrifying bacterial community revealed a core microbiome responsible for the anaerobic degradation of quinoline

Quinoline is biodegradable under anaerobic conditions, but information about the degradation kinetics and the involved microorganisms is scarce. Here, the dynamics of a quinoline-degrading bacterial consortium were studied in anoxic batch cultures containing nitrate. The cultures removed 83.5% of the quinoline during the first 80 hours, which were dominated by denitrification, and then switched to methanogenesis when the nitrogen oxyanions were depleted. Time-resolved community analysis using pyrosequencing revealed that denitrifiying bacteria belonging to the genus Thauera were enriched during the denitrification stage from 12.2% to 38.8% and 50.1% relative abundance in DNA and cDNA libraries, respectively. This suggests that they are key organisms responsible for the initial attack on quinoline. Altogether, 13 different co-abundance groups (CAGs) containing 76 different phylotypes were involved, directly or indirectly, in quinoline degradation. The dynamics of these CAGs show that specific phylotypes were associated with different phases of the degradation. Members of Rhodococcus and Desulfobacterium, as well as Rhodocyclaceae- and Syntrophobacteraceae-related phylotypes, utilized initial metabolites of the quinoline, while the resulting smaller molecules were used by secondary fermenters belonging to Anaerolineae. The concerted action by the different members of this consortium resulted in an almost complete anaerobic mineralization of the quinoline.

Evaluation of Lactobacillus casei ATCC 393 protective effect against spoilage of probiotic dry-fermented sausages

Abstract The aim of the present study was to investigate potential protective effects of both free and immobilized Lactobacillus casei ATCC 393 on wheat grains against spoilage and pathogenic microbes in probiotic dry-fermented sausages containing reduced or negligible amounts of curing salts. The results showed that the probiotic cultures resulted in significant increase of self-life and the resistance to spoilage was more prominent in samples containing immobilized cells. Although spoilage was mainly due to yeasts/moulds overgrowth, a drastic decrease was observed in enterobacteria, staphylococci and pseudomonads counts. Microbial diversity was further studied applying a PCR-DGGE protocol. Members of Lactobacillus, Lactococcus, Saccharomyces and Kluyveromyces and Debaryomyces hansenii or Priceomyces carsonii were the main microbial populations detected. Noticeably, members of Rhodococcus, Saccharothrix or Micromonospora were only detected in sausages produced with no starter culture. Microbiological and strain-specific multiplex PCR analysis confirmed that the levels of L. casei ATCC 393 in all probiotic samples after 71 days of ripening ranged above the minimum concentration for conferring a probiotic effect (≥6 log cfu/g).

Biodegradation of 2,4,6-trinitrophenol by Rhodococcus sp. isolated from a picric acid-contaminated soil

A picric acid-degrading bacterium, strain NJUST16, was isolated from a soil contaminated by picric acid and identified as a member of Rhodococcus sp. based on 16S rRNA sequence. The degradation assays suggested that the strain NJUST16 could utilize picric acid as the sole source of carbon, nitrogen and energy. The isolate grew optimally at 30 degrees C and initial pH 7.0-7.5 in the mineral salts medium supplemented with picric acid. It was basically consistent with degradation of picric acid by the isolate. Addition of nitrogen sources such as yeast extract and peptone accelerated the degradation of picric acid. However, the stimulation was concentration dependent. The degradation was accompanied by release of stoichiometric amount of nitrite and acidification. The degradation of picric acid at relatively high concentrations (>3.93 mM) demonstrated that the degradation was both pH and nitrite dependent. Neutral and slightly basic pH was crucial to achieve high concentrations of picric acid degradation by the NJUST16 strain.

The microbial community in a 2,4-dinitrophenol-digesting reactor as revealed by 16S rDNA gene analysis

The microbial community of a 2,4-dinitrophenol-digesting reactor was investigated using different molecular biological techniques based on 16S rDNA gene sequences. A PCR-denaturing gradient gel electrophoresis (DGGE) analysis of the bacterial community in the reactor showed that one strong and five minor bands were observed in the DGGE profile. The results of excising and sequencing DGGE bands suggested that members of Rhodococcus, Nocardioides, and Nitrospira species were present in the reactor. Partial sequencing of cloned 16S rDNAs revealed diversity among the six main divisions - the α, δ subclasses of Proteobacteria, Nitrospira, Cytophagal Flexibacter/Bacteroides, Verrucomicrobia, and Actinobacteria — in the reactor. Two cloned sequence types were not closely affiliated with any described bacterial divisions. The isolation and phylogenetic analysis of 2,4-DNP-degrading bacteria from the reactor revealed that isolated strains were classified into two types of bacteria having different 16S rDNA sequences. One of these strain types was identified as a relative of Rhodococcus koreensis, and the other was identified as a relative of Nocardioides simplex FJ21-A.