The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading bacterium Achromobacter xylosoxidans subsp. denitrificans strain EST4002 contains plasmid pEST4011. This plasmid ensures its host a stable 2,4-D ؉ phenotype. We determined the complete 76,958-bp nucleotide sequence of pEST4011. This plasmid is a deletion and duplication derivative of pD2M4, the 95-kb highly unstable laboratory ancestor of pEST4011, and was self-generated during different laboratory manipulations performed to increase the stability of the 2,4-D ؉ phenotype of the original strain, strain D2M4(pD2M4). The 47,935-bp catabolic region of pEST4011 forms a transposon-like structure with identical copies of the hybrid insertion element IS1071::IS1471 at the two ends. The catabolic regions of pEST4011 and pJP4, the best-studied 2,4-D-degradative plasmid, both contain homologous, tfd-like genes for complete 2,4-D degradation, but they have little sequence similarity other than that. The backbone genes of pEST4011 are most similar to the corresponding genes of broad-host-range self-transmissible IncP1 plasmids. The backbones of the other three IncP1 catabolic plasmids that have been sequenced (the 2,4-D-degradative plasmid pJP4, the haloacetate-catabolic plasmid pUO1, and the atrazinecatabolic plasmid pADP-1) are nearly identical to the backbone of R751, the archetype plasmid of the IncP1 ␤ subgroup. We show that despite the overall similarity in plasmid organization, the pEST4011 backbone is sufficiently different (51 to 86% amino acid sequence identity between individual backbone genes) from the backbones of members of the three IncP1 subgroups (the ␣, ␤, and ␥ subgroups) that it belongs to a new IncP1subgroup, the ␦ subgroup. This conclusion was also supported by a phylogenetic analysis of the trfA2, korA, and traG gene products of different IncP1 plasmids.Microbial degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a xenobiotic herbicide used worldwide for almost 60 years, is a well-studied process. Various soil bacteria can use 2,4-D as a carbon and energy source. Therefore, this compound has become a model for studying the evolution and distribution of genes for the degradation of chloroaromatic compounds. A number of bacterial strains belonging to different phylogenetic groups able to mineralize this compound have been found to possess genetically and enzymatically different 2,4-D-catabolic pathways (9,10,(16)(17)(18). The best-studied 2,4-D degradation genes (located in a chromosome or a plasmid) are tfd-like (pJP4-like). The very recently sequenced 87,688-bp plasmid pJP4 (48) from Wautersia eutropha JMP134 (formerly Ralstonia eutropha) was originally isolated in Australia (8), and its tfd genes and the corresponding enzymes responsible for converting 2,4-D to 3-oxoadipate are well characterized (22,23,25,26,35,58). Besides pJP4, there are only two cases in which the DNA regions containing tfd genes for the whole 2,4-D degradation pathway have been sequenced, a chromosomal transposon-like structure (about 30 kb) from Delftia acidovor...

Endophytes are microbes and fungi that live inside plant tissues without damaging the host. Herein we examine the dynamic changes in the endophytic bacterial community in potato (Solanum tuberosum) tuber in response to pathogenic infection by Pectobacterium atrosepticum, which causes soft rot in numerous economically important crops. We quantified community changes using both cultivation and next-generation sequencing of the 16S rRNA gene and found that, despite observing significant variability in both the mass of macerated tissue and structure of the endophytic community between individual potato tubers, P. atrosepticum is always taken over by the endophytes during maceration. 16S rDNA sequencing revealed bacteria from the phyla Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, Fusobacteria, Verrucomicrobia, Acidobacteria, TM7, and Deinococcus-Thermus. Prior to infection, Propionibacterium acnes is frequently among the dominant taxa, yet is out competed by relatively few dominant taxa as the infection proceeds. Two days post-infection, the most abundant sequences in macerated potato tissue are Gammaproteobacteria. The most dominant genera are Enterobacter and Pseudomonas. Eight days post-infection, the number of anaerobic pectolytic Clostridia increases, probably due to oxygen depletion. These results demonstrate that the pathogenesis is strictly initiated by the pathogen (sensu stricto) and proceeds with a major contribution from the endophytic community.

Two Gram-negative, motile, aerobic bacterial strains, designated B2T and 1_C16_27T, were respectively isolated from a seawater sample collected from the East China Sea and a semi-coke sample from north-eastern Estonia. Their genetic, phenotypic and chemotaxonomic properties were studied. The isolates were short rods with polar flagella and were positive for catalase and oxidase activities. Q-10 was the predominant respiratory ubiquinone. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and two unidentified glycolipids. The major fatty acids were nonadecanoic (C19 : 0 cyclo), octadecanoic (C18 : 0 and C18 : 0 3-OH), octadecenoic (C18 : 1) and hexadecanoic (C16 : 0) acids. The G+C content of the genomic DNA was 58.1–59.3 mol%. 16S rRNA gene sequence analysis revealed that the two isolates represent a distinct lineage within the family Hyphomicrobiaceae. The phylogenetically closest relatives were Cucumibacter (92.7–93.7 % 16S rRNA gene sequence similarity), Devosia (92.9–94.4 %) and Zhangella (91.7–92.1 %). Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, revealed that strains B2T and 1_C16_27T could be differentiated from each other and from members of the genera Cucumibacter, Devosia and Zhangella. Therefore, it is proposed that strains B2T and 1_C16_27T represent two novel species in a new genus, for which the names Pelagibacterium halotolerans gen. nov., sp. nov. (the type species; type strain B2T  = CGMCC 1.7692T  = JCM 15775T) and Pelagibacterium luteolum sp. nov. (type strain 1_C16_27T  = CGMCC 1.10267T  = JCM 16552T  = CELMS EEUT 1C1627T) are proposed.

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Phenol- and p-cresol-degrading pseudomonads isolated from phenol-polluted water were analysed by the sequences of a large subunit of multicomponent phenol hydroxylase (LmPH) and catechol 2,3-dioxygenase (C23O), as well as according to the structure of the plasmid-borne pheBA operon encoding catechol 1,2-dioxygenase and single component phenol hydoxylase. Comparison of the carA gene sequences (encodes the small subunit of carbamoylphosphate synthase) between the strains showed species- and biotype-specific phylogenetic grouping. LmPHs and C23Os clustered similarly in P. fluorescens biotype B, whereas in P. mendocina strains strong genetic heterogeneity became evident. P. fluorescens strains from biotypes C and F were shown to possess the pheBA operon, which was also detected in the majority of P. putida biotype B strains which use the ortho pathway for phenol degradation. Six strains forming a separate LmPH cluster were described as the first pseudomonads possessing the Mop type LmPHs. Two strains of this cluster possessed the genes for both single and multicomponent PHs, and two had genetic rearrangements in the pheBA operon leading to the deletion of the pheA gene. Our data suggest that few central routes for the degradation of phenolic compounds may emerge in bacteria as a result of the combination of genetically diverse catabolic genes.