( 2011 )
Pseudomonas deceptionensis sp. nov., a psychrotolerant bacterium from the Antarctic.
PMID : 21062736 : DOI : 10.1099/ijs.0.024919-0 DOI : 10.1099/ijs.0.024919-0
During the taxonomic investigation of cold-adapted bacteria from samples collected in the Antarctic area of the South Shetland Islands, one Gram-reaction-negative, psychrotolerant, aerobic bacterium, designated strain M1(T), was isolated from marine sediment collected on Deception Island. The organism was rod-shaped, catalase- and oxidase-positive and motile by means of a polar flagellum. This psychrotolerant strain grew at temperatures ranging from -4 �XC to 34 �XC. Phylogenetic studies based on 16S rRNA gene sequences confirmed that Antarctic isolate M1(T) was a member of the genus Pseudomonas and was located in the Pseudomonas fragi cluster. 16S rRNA gene sequence similarity values were >98 % between 13 type strains belonging to the Pseudomonas fluorescens lineage. However, phylogenetic analysis of rpoD gene sequences showed that strain M1(T) exhibited high sequence similarity only with respect to Pseudomonas psycrophila (97.42 %) and P. fragi (96.40 %) and DNA-DNA hybridization experiments between the Antarctic isolate M1(T) and the type strains of these two closely related species revealed relatedness values of 58 and 57 %, respectively. Several phenotypic characteristics, together with the results of polar lipid and cellular fatty acid analyses, were used to differentiate strain M1(T) from related pseudomonads. Based on the evidence of this polyphasic taxonomic study, strain M1(T) represents a novel species, for which the name Pseudomonas deceptionensis sp. nov. is proposed. The type strain is M1(T) (= LMG 25555(T) = CECT 7677(T)).
( 2015 )
A novel pathway producing dimethylsulphide in bacteria is widespread in soil environments.
PMID : 25807229 : DOI : 10.1038/ncomms7579
The volatile compound dimethylsulphide (DMS) is important in climate regulation, the sulphur cycle and signalling to higher organisms. Microbial catabolism of the marine osmolyte dimethylsulphoniopropionate (DMSP) is thought to be the major biological process generating DMS. Here we report the discovery and characterization of the first gene for DMSP-independent DMS production in any bacterium. This gene, mddA, encodes a methyltransferase that methylates methanethiol and generates DMS. MddA functions in many taxonomically diverse bacteria including sediment-dwelling pseudomonads, nitrogen-fixing bradyrhizobia and cyanobacteria, and mycobacteria including the pathogen Mycobacterium tuberculosis. The mddA gene is present in metagenomes from varied environments, being particularly abundant in soil environments, where it is predicted to occur in up to 76% of bacteria. This novel pathway may significantly contribute to global DMS emissions, especially in terrestrial environments and could represent a shift from the notion that DMSP is the only significant precursor of DMS.
( 2012 )
Concordance between whole-cell matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry and multilocus sequence analysis approaches in species discrimination within the genus Pseudomonas.
PMID : 23140936 : DOI : 10.1016/j.syapm.2012.08.007
Multilocus sequence analysis (MLSA) is one of the most accepted methods for the phylogenetic assignation of Pseudomonas strains to their corresponding species. Furthermore, updated databases are essential for correct bacterial identification and the number of Pseudomonas species is increasing continuously. Currently, 127 species are validly described in Euz?by's List of Species with Standing in Nomenclature, and 29 novel species have been described since the publication of the last comprehensive MLSA phylogenetic study based on the sequences of the 16S rDNA, gyrB, rpoB and rpoD genes. Therefore, an update of the sequence database is presented, together with the analysis of the phylogeny of the genus Pseudomonas. Whole-cell matrix-assisted laser-desorption/ionization time-of-flight (WC-MALDI-TOF) mass spectrometry (MS) analysis has been applied very recently to the identification of bacteria and is considered to be a fast and reliable method. A total of 133 type strains of the recognized species and subspecies in the genus Pseudomonas, together with other representative strains, were analyzed using this new technique, and the congruence between the WC-MALDI-TOF MS and MLSA techniques was assessed for the discrimination and correct species identification of the strains. The utility of both methods in the identification of environmental and clinical strains is discussed.