Isolation and sequence analysis of a small cryptic plasmid pRK10 from a corrosion inhibitor degrading strain Serratia marcescens ACE2

Isolation and sequence analysis of pCS36-4CPA, a small plasmid from Citrobacter sp. 36-4CPA

A small plasmid designated pCS36-4CPA with a size of 5217 base pairs and G-C content of 50.74% was isolated from Citrobacter sp. 36-4CPA. The origin of replication (ori) of the plasmid was identified as a region of about 800 bp in length with an identity of 67.1% to the ColE1 plasmid at the nucleotide level. The replication region contained typical elements of ColE1-like plasmids: RNA I and RNA II with their corresponding -10 and -35 boxes, a single-strand initiation site (ssi), and a lagging-strand termination site (terH). As seen in other ColE1-like plasmids, pCS36-4CPA carried mobilisation machinery that include mobABCD genes but it did not possess the rom gene. Analysis of the multimer resolution site (mrs) was performed and XerC and XerD binding sites were identified. Also, the 70-nt transcript Rcd of pCS36-4CPA was predicted and similarity of the transcript's secondary structure with those of the ColE1-family was shown. The cargo module of pCS36-4CPA contained three open reading frames (ORFs). Two of them (ORF5 and ORF6) showed no significant homology to any known gene sequences but contained putative THAP DNA-binding (DBD) and type II restriction endonuclease EcoO109I domains. The seventh open reading frame (ORF7) encodes YhdJ-like DNA modification methylase. The region highly homologous to pCS36-4CPA was found in the Salmonella phage SE2 genome.

Assessment of 2,4-Di-tert-butylphenol induced modifications in extracellular polymeric substances of Serratia marcescens

Extracellular polymeric substances (EPS) play crucial roles in biofilm formation and biocorrosion resulting in heavy economic loss in an industrial setup. Hence, in an attempt to develop an agent to control the EPS across the hosts, the ability of 2,4-Di-tert-butylphenol (DTBP), a potent antioxidant, to modify the EPS of Serratia marcescens has been investigated in this study using biophysical methods. Protein, polysaccharides and eDNA components of EPS were inhibited significantly (p < 0.05) upon exposure to DTBP. DTBP treatment reduced the crystallite size and crystallinity index of EPS and increased the dislocation density of crystallites without inducing stress, besides increasing the hydration of EPS which reduced its thermal stability. On the whole, this study highlights the efficacy of DTBP to modulate secreted EPS of S. marcescens which in turn could facilitate the disruption of biofilms besides favouring the diffusion of antimicrobials into the cell aggregates resulting eradication of persistent biofilms.

Molecular characterization of plasmid pMbo4.6 of Moraxella bovis ATCC 10900

We report the characterization of a small cryptic plasmid unlike any previously described from Moraxella bovis ATCC 10900, a Gram-negative bacterium belonging to the family Moraxellaceae. The complete nucleotide sequence of the plasmid pMbo4.6 was determined. The plasmid was analyzed and found to be 4658 in size with a G+C content of 38.6 mol %. Computer analysis of the sequence data revealed four major open reading frames encoding putative proteins of 10.1 (ORF1), 64.2 (ORF2), 45.7 (ORF3), and 12.1 kDa (ORF4). ORF1 and ORF2 encode proteins that show a high level of amino acid sequence similarity (44 %) with some mobilization proteins. ORF3 encodes a protein showing a relatively high amino acid sequence similarity (about 40 %) with several plasmid replication initiator proteins. Upstream of ORF3, a 320-bp intergenic region, constituting the putative origin of replication that contained an AT-rich region followed by four direct repeats, was identified. This set of repeated sequences resembles iteron structures and plays an important role in the control of plasmid replication by providing a target site for the initiation of transcription and replication factors (IHF and RepA). Several palindromic sequences, inverted repeats, and hairpin-loop structures, which might confer regulatory effects on the replication of the plasmid, were also noted. ORF4 encodes an uncharacterized protein, conserved in bacteria, belonging to the DUF497 family. Sequence analysis and structural features indicate that pMbo4.6 replicates by a theta mechanism.

Unraveling the role of the rssC gene of Serratia marcescens by atomic force microscopy

The product and direct role of the rssC gene of Serratia marcescens is unknown. For unraveling the role of the rssC gene, atomic force microscopy has been used to identify the surfaces of intact S. marcescens wild-type CH-1 cells and rssC mutant CH-1ΔC cells. The detailed surface topographies were directly visualized, and quantitative measurements of the physical properties of the membrane structures were provided. CH-1 and CH-1ΔC cells were observed before and after treatment with lysozyme, and their topography-related parameters, e.g., a valley-to-peak distance, mean height, surface roughness, and surface root-mean-square values, were defined and compared. The data obtained suggest that the cellular surface topography of mutant CH-1ΔC becomes rougher and more precipitous than that of wild-type CH-1 cells. Moreover, it was found that, compared with native wild-type CH-1, the cellular surface topography of lysozyme-treated CH-1 was not changed profoundly. The product of the rssC gene is thus predicted to be mainly responsible for fatty-acid biosynthesis of the S. marcescens outer membrane. This study represents the first direct observation of the structural changes in membranes of bacterial mutant cells and offers a new prospect for predicting gene expression in bacterial cells.

Nucleotide sequence of the Serratia entomophila plasmid pADAP and the Serratia proteamaculans pU143 plasmid virulence associated region

Some strains of Serratia entomophila and S. proteamaculans cause amber disease of the New Zealand grass grub Costelytra zealandica (Coleoptera: Scarabaeidae), an important pasture pest in New Zealand. The disease determinants of S. entomophila, are encoded on a 153,404-bp plasmid, termed pADAP for amber disease associated plasmid. The S. proteamaculans strain 143 (Sp143) exhibits an unusual pathotype, where only 60-70% of C. zealandica larvae infected with the bacterium succumb to disease. DNA sequence analysis of the Sp143 pU143 virulence associated region identified high DNA similarity to the pADAP sep virulence associated region, with DNA sequence variation in the sepA gene and the variable region of the sepC component. No pADAP anti-feeding prophage orthologue was detected in the Sp143 genome. The region of pADAP replication was cloned and found to replicate in S. entomophila but not in Escherichia coli. DNA sequence analysis of the plasmid pSG348 repA gene from the French isolate of Serratia grimesii, identified 93% DNA identity to the pADAP repA gene. A comparison of the pU143 virulence associated region with the completed pADAP nucleotide sequence is given.