[Evolution and Comparative Genomics of the pSM22 Plasmid of the IncF/MOBF12 Group].

A new plasmid, pSM22, was isolated from Serratia marcescens and sequenced. Its 43 190-bp sequence with an average GC-content of 58% contains 31 open reading frames (ORFs) which form replication, conjugation, stability, and adaptive modules. The replication module includes a site of initiation of leading-strand synthesis in plasmid replication, a replication termination site (terC), the rep A (=repA1) and repA4 genes, and the copA sequence, which codes for an antisense RNA (asRNA). These structures are functionally integrated in an FII replicon (incompatibility group IncFII). Based on the significant differences between the FII replicon and the canonical sequences of the R plasmids R1 and NR1 (=R100=R222), pSM22 was assigned to a new subtype. The conjugation module includes 13 genes with a high identity to the genes responsible for conjugation of the F plasmid. A comparative genomic analysis showed that the conjugation modules of pSM22 and F are structurally similar. By the conjugation system and the presence of three conserved motifs in relaxase (TraI), pSM22 belongs to the F12 clade of the MOBF type. The stability module includes the resD and parA genes, which are responsible for the resolution of multimeric plasmid forms and their subsequent segregation between daughter cells. The adaptive module contains the microcin H47 (MccH47) secretion/processing and UV resistance genes. The mosaic structure of pSM22 and reductive evolution of its modules suggest high genomic plasticity for the genus Serratia. An analysis of the architecture of the pSM22 modules clarifies the evolutionary relationships among IncF/MOBF12 group plasmids in bacteria of the family Enterobacteriaceae and opens a novel avenue for further comparative genomic studies of Serratia plasmids.

[Raoultella planticola, a new strain degrading 2,4,5-trichlorophenoxyacetic acid].

A new strain that degrades the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was isolated from soil, which was exposed to factors related to the petrochemical industry. According to its physiological, biochemical, cultural, and morphological traits, together with the sequence of the 16S rRNA gene, the strain was identified as Raoultella planticola 33-4ch. The strain could consume 2,4,5-T as a sole source of carbon and energy. The amount of 2,4,5-T in the culture medium decreased by 51% after five days of incubation. Raoultella planticola 33-4ch consumes 2,4,5-T to produce 4-chlorophenoxyacetic, phenoxyacetic, and 3-methyl-2,6-dioxo-4-hexenoic acids.

[Identification and characterization of a plasmid in strain Aeronomas hydrophila IBRB-36 4CPA carrying genes for catabolism of chlorophenoxyacetic acids]. / Identifikatsiia i kharakteristika plazmidy shtamma Aeronomas hydrophila 1BRB-36 4CPA, nesushchei geny katabolizma khlorfenoksiukusnykh kislot.

Results of studying plasmid pAH36 in strain Aeronomas hydrophila IBRB-36 4CPA are presented. Plasmid pAH36 possesses BamHI, PstI, and HindIII restriction sites and is 5.4 kb in size. The plasmid was shown to contain genes for catabolism of chlor-substituted phenoxyacetic acids.