The biosynthesis of Peps, a lanthionine-containing antimicrobial peptide, is directed by the 20-kbp plasmid pED503. We identified a 7.9-kbp DNA-fragment within this plasmid which covers the information for Peps synthesis in the homologous host Staphylococcus epidermidis S which has been cured of pED503. This fragment contained, in addition to the previously described structural gene pepA and the immunity gene pep1 [Reis, M., Eschbach-Bludau, M., Iglesias-Wind, M. I., Kupke, T. & Sahl, H . 4 . (1994) Appl. Env. Microbiol. 60, 2876-28831, a genepepTcoding for a translocator of the ABC transporter family, a gene pepP coding for a serine protease and two genes pepB and pepC coding for putative modification enzymes ; the gene arrangement is pepTIAPBC. We analyzed the biosynthetic genes with respect to their function in Peps biosynthesis. Deletion of PepT reduced Pep5 production to about lo%, indicating that it can be partially replaced by other host-encoded translocators. Inactivation of PepP by site-directed mutagenesis of the active-site His residue resulted in production of incorrectly pi-ocessed Peps fragments with strongly reduced antimicrobial activity. Deletion of pepB and pepC leads to accumulation of Pep5 prepeptide in the cells without excretion of processed peptide. A pepC-deletion clone did not excrete correctly matured Peps but it did produce fragments from which serine and threonine were absent. Only one of these fragments contained a single lanthionine residue out of three expected while the remaining, unmodified cysteine residues could be detected by reaction with Ellman's reagent. These results demonstrate that PepC is a thioether-forming protein and strongly suggest that PepB is responsible for dehydration of serine and threonine.Keywords: lantibiotics ; Peps biosynthetic gene cluster; PepC, thioether-forming enzyme; PepP, serine protease.Peps is a tricyclic peptide produced by Staphylococcus epidermidis S (Sahl and Brandis, 1981) which belongs to the family of lantibiotics, a designation introduced to characterize lanthionine containing peptides with antimicrobial activity (Schnell et al., 1988). In contrast to conventional peptide antibiotics, which are synthesized by multienzyme complexes, lantibiotics derive from gene-encoded precursor peptides. These precursors consist of a leader sequence and a propeptide part which is posttranslationally modified to give the mature lantibiotic. It was proposed that in a first modification step the serine and threonine residues of the propeptide part are dehydrated to didehydroalanine (Dha) and didehydrobutyrine (Dhb) (Schnell et al., 1988). Such dehydrated prepeptides have been isolated from S. epidermidis 5 (Weil et al., 1990). In a second step thiol groups of cysteine Note. The novel nucleotide sequence data published here have been deposited with the EMBL sequence data bank and are available under accession number 249865. The novel amino acid sequence data have also been deposited with the EMBL sequence data bank. residues react with the double bonds of ...

Sequences of the 16s rDNA from all available type strains of Chromatium species have been determined and were compared to those of other Chromatiaceae, a few selected Ectothiorhodospiraceae and Escherichia coli. The clear separation of Ectothiorhodospiraceae and Chromatiaceae is confirmed. Most significantly the sequence comparison revealed a genetic divergence between Chromatium species originated from freshwater sources and those of truly marine and halophilic nature. Major phylogenetic branches of the Chromatiaceae contain (i) marine and halophilic species, (ii) freshwater Chromatium species together with Thiocystis species and (iii) species of the genera Thiocapsa and Amoebobacter as recently reclassified [Guyoneaud, R. & 6 other authors (1998). lnt J Syst Bacteriol48, 957-9641, namely Thiocapsa roseopersicina, Thiocapsa pendens (formerly Amoebobacter pendens), Thiocapsa rosea (formerly Amoebobacter roseus), Amoebobacter purpureus and Thiolamprovum pedioforme (formerly Amoebobacter pedioformis). The genetic relationships between the species and groups are n o t in congruence with the current classification of the Chromatiaceae and a reclassification is proposed on the basis of 16s rDNA sequence similarity supported by selected phenotypic properties. The proposed changes include the transfers of Chromatium minus and Chromatium violascens to Thiocystis minor comb. nov. and Thiocystis violascens com b. nov., of Chromatium vinosum, Chromatium minutissimum and Chromatium warmingii t o the new genus Allochromatium as Allochromatium vinosum comb. nov., Allochromatium minutissimum comb. nov., and Allochromatium warmingii comb. nov., of Chromatium tepidum t o the new genus Thermochromatium as Thermochromatium tepidum comb. nov., of Chromatium salexigens and Chromatium glycolicum to the new genus Halochromatium as Halochromatium salexigens comb. nov. and Halochromatium glycolicum com b. nov., o f Chromatium gracile and Chromatium purpuratum to the new genus as Marichromatium gracile comb. nov. and Marichromatium purpuratum comb. nov., of Thiocapsa pfennigii t o Thiococcus pfennigii gen. nom. rev., of Thiocapsa halophila t o the new genus Thiohalocapsa as Thiohalocapsa halophila comb. nov., and of Chromatium buderi t o the new genus lsochromatium as lsochromatium buderi comb. nov. ~

[1] The effect of volcanic activity on submarine hydrothermal systems has been well documented along fast-and intermediate-spreading centers but not from slow-spreading ridges. Indeed, volcanic eruptions are expected to be rare on slow-spreading axes. Here we report the presence of hydrothermal venting associated with extremely fresh lava flows at an elevated, apparently magmatically robust segment center on the slow-spreading southern Mid-Atlantic Ridge near 5°S. Three high-temperature vent fields have been recognized so far over a strike length of less than 2 km with two fields venting phase-separated, vapor-type fluids. Exit temperatures at one of the fields reach up to 407°C, at conditions of the critical point of seawater, the highest temperatures ever recorded from the seafloor. Fluid and vent field characteristics show a large variability between the vent fields, a variation that is not expected within such a limited area. We conclude from mineralogical investigations of hydrothermal precipitates that vent-fluid compositions have evolved recently from relatively oxidizing to more reducing conditions, a shift that could also be related to renewed magmatic activity in the area. Current high exit temperatures, reducing conditions, low silica contents, and high hydrogen contents in the fluids of two vent sites are consistent with a shallow magmatic source, probably related to a young volcanic eruption event nearby, in which basaltic magma is actively crystallizing. This is the first reported evidence for direct magmatic-hydrothermal interaction on a slow-spreading mid-ocean ridge.Components: 8945 words, 9 figures, 3 tables.Keywords: mid-ocean ridge; eruption; vent fauna; fluids; phase separation.Index Terms: 1032 Geochemistry: Mid-oceanic ridge processes (3614, 8416); 0450 Biogeosciences: Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424); 1034 Geochemistry: Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424). Haase, K. M., et al. (2007), Young volcanism and related hydrothermal activity at 5°S on the slow-spreading southern Mid-

Sequences of the 16S rRNA gene were determined from all type strains of the recognized Ectothiorhodospira species and from a number of additional strains. For the first time, these data resolve the phylogenetic relationships of the Ectothiorhodospiraceae in detail, confirm the established species, and improve the classification of strains of uncertain affiliation. Two major groups that are recognized as separate genera were clearly established. The extremely halophilic species were removed from the genus Ectothiorhodospira and reassigned to the new genus Halorhodospira gen. nov., to recognize that the most halophilic eubacteria are species of this genus. These species are Halorhodospira halophila comb. nov., Halorhodospira halochloris comb. nov., and Halorhodospira abdelmalekii comb. nov. Among the slightly halophilic Ectothiorhodospira species, the classification of strains belonging to Ectothiorhodospira mobilis and Ectothiorhodospira shaposhnikovii was improved. Several strains that were tentatively identified as Ectothiorhodospira mobilis form a separate cluster on the basis of their 16S rDNA sequences and are recognized as two new species: Ectothiorhodospira haloalkaliphila sp. nov., which includes the most alkaliphilic strains originating from strongly alkaline soda lakes, and Ectothiorhodospira marina, describing isolates from the marine environment.