T. thermophilus HB27 is naturally competent to both linear and circular DNA, and DNA transport mechanisms in this species have been well studied [69,70]. The genome of T. oshimai Cabozantinib price JL-2 and T. thermophilus JL-18 both contain homologs of DNA transport genes (Table 5), suggesting that both T. oshimai JL-2 and T. thermophilus JL-18 are naturally competent. Table 5 Identification of competence proteins in T. oshimai JL-2 and T. thermophilus JL-18 by IMG/ER [71].? Conclusions We report the finished genomes of T. oshimai JL-2 and T. thermophilus JL-18. T. oshimai JL-2 is the first complete genome to be reported for this species, while T. thermophilus JL-18 is the fourth genome to be reported for T. thermophilus.
Analysis of the genomes revealed that they encode enzymes for the reduction of nitrate to nitrous oxide, which is consistent with the high flux of nitrous oxide reported in GBS [6], and explains the truncated denitrification phenotype reported for many Thermus isolates obtained from that system [6]. It is intriguing that Thermus scotoductus SA-01 also has genes encoding the sequential reduction of nitrate to nitrous oxide but lacks genes encoding the nitrous oxide reductase. The high degree of synteny in the respiratory gene cluster combined with the conserved absence of the nitrous oxide reductase suggests incomplete denitrification might be a previously unrecognized but conserved feature of denitrification pathways in the genus Thermus, although T. thermophilus NAR1 appears to be capable of complete denitrification to N2 [73]. Another unusual feature of the T.
oshimai JL-2 and T. scotoductus SA-01 denitrification systems is the apparent presence of the NO-forming, Cu-containing nitrite reductase, NirK, and the isofunctional tetraheme cytochrome cd1-containing nitrite reductase, NirS. T. oshimai JL-2 and T. thermophilus JL-18 also may be capable of sulfur oxidation since they both encode a complete, chromosomal sox cluster. However, experiments with GBS sediments failed to demonstrate a stimulation of denitrification when thiosulfate was added in excess [74], suggesting thiosulfate oxidation may not be coupled to denitrification in these organisms. The presence of psrA, psrB and psrC genes encoding polysulfide reducatase in T. oshimai JL-2 suggests the ability to reduce polysulfide. The function of these putative pathways could be tested with pure cultures in the laboratory.
The presence of complete macromolecular machinery for natural competence and the presence of megaplasmids harboring genes for nitrate/nitrite reduction and thermophily Anacetrapib points out that T. oshimai JL-2 and T. thermophilus JL-18 could have acquired innumerable genes through intra- and inter-domain gene transfer, and suggests considerable plasticity in denitrification pathways.