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ABSTRACT: Development of novel antibacterial agents is required to control infection with multidrug-resistant Streptococcus suis. HolSMP and LySMP, the holin and lysin of S. suis serotype 2 bacteriophage, named SMP, are responsible for lysis of host cells and release of progeny phage. HolSMP and LySMP expressed in Escherichia coli BL21(DE3) exerted efficient activity at 37 °C, pH 5.2, with addition of 0.8 % β-mercaptoethanol. Lytic spectra of purified HolSMP, LySMP or HolSMP + LySMP mixture were investigated. HolSMP, exhibiting a narrow lytic spectrum, was effective against Staphylococcus aureus and Bacillus subtilis, which were insensitive to LySMP. Moreover, HolSMP was identified as a promising antibacterial agent which was able to extend the spectrum of LySMP. The data suggest that combined use of holin and lysin could be a candidate strategy for resolution of drug resistance.
Current Microbiology 04/2012; 65(1):28-34. · 1.82 Impact Factor
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ABSTRACT: Holins are a group of phage-encoded membrane proteins that control access of phage-encoded endolysins to the peptidoglycan, and thereby trigger the lysis process at a precise time point as the 'lysis clock'. SMP is an isolated and characterized Streptococcus suis lytic phage. The aims of this study were to determine the holin gene, HolSMP, in the genome of SMP, and characterized the function of holin, HolSMP, in phage infection.
HolSMP was predicted to encode a small membrane protein with three hydrophobic transmembrane helices. During SMP infections, HolSMP was transcribed as a late gene and HolSMP accumulated harmlessly in the cell membrane before host cell lysis. Expression of HolSMP in Escherichia coli induced an increase in cytoplasmic membrane permeability, an inhibition of host cell growth and significant cell lysis in the presence of LySMP, the endolysin of phage SMP. HolSMP was prematurely triggered by the addition of energy poison to the medium. HolSMP complemented the defective λ S allele in a non-suppressing Escherichia coli strain to produce phage plaques.
Our results suggest that HolSMP is the holin protein of phage SMP and a two-step lysis system exists in SMP.
Virology Journal 03/2012; 9:70. · 2.34 Impact Factor
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ABSTRACT: The holin-lysin two-step lysis system widely exists in double stranded DNA bacteriophages for the release of progeny bacteriophage from an infected bacterial cell at the final stage of phage infection. Lambda bacteriophage is a prototype for studying holin. The S gene in Lambda bacteriophage has a dual-start motif and encodes holin S105 and antiholin S107. Here, we reviewed the progress in topological structure of holin from Lambda bacteriophage and its formation of membrane lethal holes. We also discussed the potential of the holin in the control of bacterial infection.
ACTA MICROBIOLOGICA SINICA 02/2012; 52(2):141-5.
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ABSTRACT: Bacterial biofilms are crucial to the pathogenesis of many important infections and are difficult to eradicate. Streptococcus suis is an important pathogen of pigs, and here the biofilm-forming ability of 32 strains of this species was determined. Significant biofilms were completely formed by 10 of the strains after 60 h of incubation, with exopolysaccharide production in the biofilm significantly higher than that in the corresponding planktonic cultures. S. suis strain SS2-4 formed a dense biofilm, as revealed by scanning electron microscopy, and in this state exhibited increased resistance to a number of antibiotics (ampicillin, amoxicillin, ciprofloxacin, kanamycin, and rifampin) compared to that of planktonic cultures. A bacteriophage lysin, designated LySMP, was used to attack biofilms alone and in combination with antibiotics and bacteriophage. The results demonstrated that the biofilms formed by S. suis, especially strains SS2-4 and SS2-H, could be dispersed by LySMP and with >80% removal compared to a biofilm reduction by treatment with either antibiotics or bacteriophage alone of less than 20%; in addition to disruption of the biofilm structure, the S. suis cells themselves were inactivated by LySMP. The efficacy of LySMP was not dose dependent, and in combination with antibiotics, it acted synergistically to maximize dispersal of the S. suis biofilm and inactivate the released cells. These data suggest that bacteriophage lysin could form part of an effective strategy to treat S. suis infections and represents a new class of antibiofilm agents.
Applied and environmental microbiology 12/2011; 77(23):8272-9. · 3.69 Impact Factor
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ABSTRACT: The prevalence and nature of Shiga toxin (Stx)-producing Escherichia coli (STEC) and Stx phage were investigated in 720 swine fecal samples randomly collected from a commercial breeding pig farm in China over a 1-year surveillance period. Eight STEC O157 (1.1%), 33 STEC non-O157 (4.6%), and two stx-negative O157 (0.3%) isolates were identified. Fecal filtrates were screened directly for Stx phages using E. coli K-12 derivative strains MC1061 as indicator, yielding 15 Stx1 and 57 Stx2 phages. One Stx1 and eight Stx2 phages were obtained following norfloxacin induction of the eight field STEC O157 isolates. All Stx1 phages had hexagonal heads with long tails, while Stx2 phages had three different morphologies. Notably, most of field STEC O157 isolates released more free phages and Stx toxin after induction with ciprofloxacin. Furthermore, upon infection with the recombinant phage ΦMin27(Δstx::cat), E. coli laboratory strains produced both lysogenic and lytic phage, whereas two of the eight O157 STEC isolates produced only lysogens. The lysogens from laboratory strains produced infectious particles similar to ΦMin27. Similarly, the lysogens from the STEC O157 isolates released Stx phage too, although free ΦMin27(Δstx::cat) particles were not detected. Collectively, our results reveal that breeding pig farms could be important reservoirs for Stx phages and that residual antibacterial agents may enhance the release of Stx phages and the expression of Stx.
Current Microbiology 02/2011; 62(2):458-64. · 1.82 Impact Factor
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ABSTRACT: We studied biologic characteristics of Stx2-converting phage induced from Escherichia coli O157 by mitomycin C.
Eight Stx2-converting phages were isolated from E. coli O157 and identified by PCR. The phage particles were purified and phage DNA was extracted. Random priming digoxin (DIG)-labeled stx2-specific gene probe was prepared for Southern blot. The morphology of these phages were studied by electron microscopy. Protein profiles were analyzed by Sodium Dodecyl Sulphate PolyAcrylamide Gel Electrophoresis (SDS-PAGE). Restriction fragment length polymorphism (RFLP) was used to confirm the size, type, and polymorphism of the purified phage genome.
These 8 phages were confirmed Stx2-converting phage and DIG-labeled probe was highly specific. All phages had a regular hexagonal head and a short tail, belonging to Podoviridae phage families. The Stx2 phages had genome sizes in the range of 48 to 65.3kb, consisting of double-stranded DNA. The restriction fragment length polymorphism of these phages showed different groups, although the SDS-PAGE protein profiles of these phages were similar.
These 8 Stx2-converting phages with similar morphology belonged to Podoviridae phage families. The protein profiles were highly identical. We could differentiate these Stx2-converting phages according to their restriction fragment length polymorphism patterns.
ACTA MICROBIOLOGICA SINICA 09/2008; 48(8):1121-5.
