Hydrogen production in anaerobic and microaerobic Thermotoga neapolitana.

We have tested the hypothesis (Van Ooteghem et al. Appl Biochem Biotechnol 2002 98-100: 177-189) that microaerobic metabolism may increase the yield of H(2) from the thermophilic bacterium Thermotoga neapolitana. In anaerobic conditions, T. neapolitana converted glucose into acetic acid and lactic acid and yielded 2.4 +/- 0.3 mol H(2) mol(-1) glucose. The bacterium tolerated low O(2) partial pressures but the H(2) yield was not improved under microaerobic conditions. Our results indicate that T. neapolitana only produces H(2) by anaerobic metabolism, and that the yield of H(2) can be maximised by minimising the production of lactic acid.

Chromosome evolution in the Thermotogales: large-scale inversions and strain diversification of CRISPR sequences.

In the present study, the chromosomes of two members of the Thermotogales were compared. A whole-genome alignment of Thermotoga maritima MSB8 and Thermotoga neapolitana NS-E has revealed numerous large-scale DNA rearrangements, most of which are associated with CRISPR DNA repeats and/or tRNA genes. These DNA rearrangements do not include the putative origin of DNA replication but move within the same replichore, i.e., the same replicating half of the chromosome (delimited by the replication origin and terminus). Based on cumulative GC skew analysis, both the T. maritima and T. neapolitana lineages contain one or two major inverted DNA segments. Also, based on PCR amplification and sequence analysis of the DNA joints that are associated with the major rearrangements, the overall chromosome architecture was found to be conserved at most DNA joints for other strains of T. neapolitana. Taken together, the results from this analysis suggest that the observed chromosomal rearrangements in the Thermotogales likely occurred by successive inversions after their divergence from a common ancestor and before strain diversification. Finally, sequence analysis shows that size polymorphisms in the DNA joints associated with CRISPRs can be explained by expansion and possibly contraction of the DNA repeat and spacer unit, providing a tool for discerning the relatedness of strains from different geographic locations.