The complete genome of the tetrachloroethene-respiring Epsilonproteobacterium Sulfurospirillum halorespirans.

Sulfurospirillum halorespirans is a bacterium that couples the reductive dehalogenation of chlorinated ethenes to growth. This process is called organohalide respiration (OHR), which can be of importance for bioremediation. Here, we report the complete genome of S. halorespirans, the second one of an organohalide-respiring Epsilonproteobacterium after that of Sulfurospirillum multivorans. With both genomes at hand, we were able to ascertain that the genomic region encoding OHR proteins in Epsilonproteobacteria differs from that found in organohalide-respiring bacteria (OHRB) affiliated to other phyla and that the production of a unique cobamide, norpseudo-B12, might not be limited to the model organism S. multivorans. The OHR region is virtually identical in both organisms with differences only in the gene sequence of the key enzyme of OHR, the PCE reductive dehalogenase (PceA), and in regulatory regions. This is of interest, since the availability of natural, closely related variants opens an avenue to study the poorly understood OHRB, which withstand systematic genetic manipulation so far.

Sequence variations of Env signal peptide alleles in different clinical stages of HIV infection.

The human immunodeficiency virus has been shown to increase its infectivity throughout the course of infection. This virus selection property has been associated with genome mutations and recombinations among virus variants, causing amino acid residue alterations in important viral proteins. In order to explore the contribution of Env signal peptide (Env-sp) to Env glycoprotein expression and its possible relationship to increased virus infectivity observed at late stages of infection, we characterized Env-sp sequences derived from twelve patients at "early" and "late" stages of HIV infection without antiretroviral therapy use. In spite of the remarkable overall similarity between both stages, we observed the deletion of a sequence of neutral and basic residues at the Env-sp amino terminus in virus from early stage specimens and the insertion of basic residues in the hydrophobic region on late-stage viral isolates. The Env-sp sequence alterations may have viral adaptive functions during HIV infection.