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The halophilic γ-proteobacterium Halomonas elongata DSM 2581T thrives at high salinity by synthesizing and accumulating the compatible solute ectoine. Ectoine levels are highly regulated according to external salt levels but the overall picture of its metabolism and control is not well understood. Apart from its critical role in cell adaptation to halophilic environments, ectoine can be used as a stabilizer for enzymes and as a cell protectant in skin and health care applications and is thus produced annually on a scale of tons in an industrial process using H. elongata as producer strain. This paper presents the complete genome sequence of H. elongata (4 061 296 bp) and includes experiments and analysis identifying and characterizing the entire ectoine metabolism, including a newly discovered pathway for ectoine degradation and its cyclic connection to ectoine synthesis. The degradation of ectoine (doe) proceeds via hydrolysis of ectoine (DoeA) to Nα-acetyl-L-2,4-diaminobutyric acid, followed by deacetylation to diaminobutyric acid (DoeB). In H. elongata, diaminobutyric acid can either flow off to aspartate or re-enter the ectoine synthesis pathway, forming a cycle of ectoine synthesis and degradation. Genome comparison revealed that the ectoine degradation pathway exists predominantly in non-halophilic bacteria unable to synthesize ectoine. Based on the resulting genetic and biochemical data, a metabolic flux model of ectoine metabolism was derived that can be used to understand the way H. elongata survives under varying salt stresses and that provides a basis for a model-driven improvement of industrial ectoine production.
A novel Gram-positive, aerobic, actinobacterial strain, CF6/1T, was isolated in 2007 during environmental screening of arid desert soil in the Sahara near to Ourba, Chad. The isolate was found to grow best in a temperature range of 20–37 °C and at pH 6.0–8.5 and showed no NaCl tolerance, forming black-coloured and nearly circular colonies on GYM agar. Chemotaxonomic and molecular characteristics determined for the isolate match those previously described for members of the genus Geodermatophilus. The DNA G + C content of the novel strain was determined to be 74.9 mol %. The peptidoglycan was found to contain meso-diaminopimelic acid as the diagnostic diamino acid. The main phospholipids were determined to be phosphatidylethanolamine, phosphatidylinositol, phosphatidylcholine, diphosphatidylglycerol and traces of phosphatidylglycerol; MK-9(H4) was identified as the dominant menaquinone and galactose as the diagnostic sugar. The major cellular fatty acids were found to be the branched-chain saturated acids iso-C16:0 and iso-C15:0, as well as C17:1ω8c. The 16S rRNA gene sequence shows 97.5–97.9 % sequence identity with the four validly named or at least effectively published members of the genus: Geodermatophilus obscurus (97.5 %), Geodermatophilus arenarius (97.7 %), Geodermatophilus ruber (97.9 %) and Geodermatophilus nigrescens (97.9 %). Based on the results from this polyphasic taxonomic analysis and DNA–DNA hybridizations with all type strains of the genus, we propose that strain CF6/1T represents a novel species, Geodermatophilus siccatus, with the type strain CF6/1T = DSM 45419T = CCUG 62765T = MTCC 11414T.
Geodermatophilus africanus sp. nov., a halotolerant actinomycete isolated from Saharan desert sand
(2013)
A novel Gram-strain positive, aerobic, actinobacterial strain, designated CF11/1T, was isolated from a sand sample obtained in the Sahara Desert, Chad. The black-pigmented isolate was aerobic and exhibited optimal growth from 25 to 35 °C at pH 6.08.0 and with 08 % (w/v) NaCl, indicating that it is a halotolerant mesophile. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The G+C content in the genome was 74.4 mol%. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diaminoacid. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and a minor fraction of phosphatidylglycerol; MK-9(H4) was the dominant menaquinone, and galactose was detected as a diagnostic sugar. The major cellular fatty acid was branched-chain saturated acid iso-C16:0. Analysis of 16S rRNA gene sequences showed 95.398.6 % pairwise sequence identity with the members of the genus Geodermatophilus. Based on phenotypic and chemotaxonomic properties, as well as phylogenetic distinctiveness, the isolate represents a novel species, Geodermatophilus africanus, with the type strain CF11/1T (DSM 45422 = CCUG 62969 = MTCC 11556).
A novel Gram-reaction-positive actinobacterial strain, designated CF5/3T, was isolated from a sand sample obtained in the Sahara Desert, Chad. The greenish-black-pigmented isolate was aerobic and exhibited optimal growth from 25–40 °C at pH 6.0–10.0 with 0–1 % (w/v) NaCl. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G+C content of the genome of the novel strain was 75.5 mol%. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diamino acid. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and a minor fraction of phosphatidylglycerol. MK-9(H4) was the dominant menaquinone, and galactose was detected as a diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids: iso-C15:0 and iso-C16:0. Analysis of 16S rRNA gene sequences showed 95.6–98.8 % pairwise sequence identity with the members of the genus Geodermatophilus. Based on phenotypic and chemotaxonomic properties, as well as phylogenetic distinctiveness, the isolate represents a novel species, Geodermatophilus normandii, with the type strain CF5/3T (=DSM 45417T=CCUG 62814T=MTCC 11412T).
A novel Gram-positive, multiloculated thalli-forming, aerobic, actinobacterial strain, CF9/1/1T, was isolated in 2007 during environmental screening for xerophilic fungi in arid desert soil from the Sahara desert, Chad. The isolate grew best at a temperature range of 20–35 °C and at pH 6.0–8.5 and with 0–4% (w/v) NaCl, forming black-coloured and irregular colonies on GYM agar. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G+C content of the novel strain was 75.4 mol%. The peptidoglycan contained meso-diaminopimelic acid as a diagnostic diamino acid. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, a not yet structurally identified aminophospholipid and a small amount of phosphatidylglycerol; MK-9(H4) was identified as the dominant menaquinone and galactose was a diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids: iso-C16:0 and iso-C15:0. The 16S rRNA gene sequence of the isolate showed 94.697.0% sequence similarities with those of five members of the genus: Geodermatophilus ruber DSM 45317T (94.6%), Geodermatophilus obscurus DSM 43160T (94.8%), Geodermatophilus siccatus DSM 45419T (96.2%), Geodermatophilus nigrescens DSM 45408T (96.7%) and Geodermatophilus arenarius DSM 45418T (97.0%). Based on the evidence from this polyphasic taxonomic study, a novel species, Geodermatophilus telluris sp. nov., is proposed; the type strain is CF9/1/1T (=DSM 45421T=CCUG 62764T).
A novel Gram-positive, aerobic, actinobacterial strain, CF5/4T, was isolated in 2007 during an environmental screening of arid desert soil in Ouré Cassoni, Chad. The isolate grew best in a temperature range of 2840 °C and at pH 6.0-8.5, with 0-1 % (w/v) NaCl, forming brown-coloured and nearly circular colonies on GYM agar. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G + C content of the novel strain was 75.9 mol %. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diaminoacid. The main phospholipids were phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, diphosphatidylglycerol and a small amount of phosphatidylglycerol; MK-9(H4) was identified as the dominant menaquinone and galactose as diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids: iso-C15:0 and iso-C16:0. The 16S rRNA gene showed 96.298.3 % sequence identity with the three members of the genus Geodermatophilus: G. obscurus (96.2 %), G. ruber (96.5 %), and G. nigrescens (98.3 %). Based on the chemotaxonomic results, 16S rRNA gene sequence analysis and DNA–DNA hybridization with the type strain of G. nigrescens, the isolate is proposed to represent a novel species, Geodermatophilus arenarius (type strain CF5/4T = DSM 45418T = MTCC 11413T = CCUG 62763T).
Three novel Gram-positive, aerobic, actinobacterial strains, CF5/2T, CF5/1 and CF7/1, were isolated in 2007 during environmental screening of arid desert soil in the Sahara desert, Chad. Results from riboprinting, MALDI-TOF protein spectra and 16S rRNA sequence analysis confirmed that all three strains belonged to the same species. Phylogenetic analysis of 16S rRNA sequences with the strains' closest relatives indicated that they represented a distinct species. The three novel strains also shared a number of physiological and biochemical characteristics distinct from previously named Geodermatophilus species. The novel strains' peptidoglycan contained meso-diaminopimelic acid; their main phospholipids were phosphatidylcholine, phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol and a small amount of phosphatidylglycerol; MK-9(H4) was the dominant menaquinone. The major cellular fatty acids were the branched-chain saturated acids iso-C16:0 and iso-C15:0. Galactose was detected as diagnostic sugar. Based on these chemotaxonomic results, 16S rRNA gene sequence analysis and DNA–DNA hybridization between strain CF5/2T and the type strains of Geodermatophilus saharensis, Geodermatophilus arenarius, Geodermatophilus nigrescens, Geodermatophilus telluris and Geodermatophilus siccatus, the isolates CF5/2T, CF5/1 and CF7/1 are proposed to represent a novel species, Geodermatophilus tzadiensis, with type strain CF5/2T = DSM 45416 = MTCC 11411 and two reference strains, CF5/1 (DSM 45415) and CF7/1 (DSM 45420).
A novel Gram-positive, aerobic, actinobacterial strain, CF5/5, was isolated from soil in the Sahara desert, Chad. It grew best at 20–35 °C and at pH 6.0–8.0 and with 0–4 % (w/v) NaCl, forming black-colored colonies. Chemotaxonomic and molecular characteristics of the isolate matched those described for members of the genus Geodermatophilus. The DNA G + C content was 75.9 mol%. The peptidoglycan contained meso-diaminopimelic acid; galactose and xylose were detected as diagnostic sugars. The main phospholipids were diphosphatidylglycerol, phosphatidylcholine, and phosphatidylinositol; MK-9(H4) was the dominant menaquinone. The major cellular fatty acids were: iso-C16:0 and iso-C15:0. The 16S rRNA gene showed 95.6–98.3 % sequence similarity with the other named members of the genus Geodermatophilus. Based on the polyphasic taxonomy data, the isolate is proposed to represent a novel species, Geodermatophilus saharensis with the type strain CF5/5T = DSM 45423 = CCUG 62813 = MTCC 11416.