Isolation, molecular identification and influence of incubation period on hemolysine gene expression in Serratia marcescens local isolates

Hemolysine gene expression in Serratia marcescens isolates

Abstract

One hundred samples were collected from clinical and environmental sources in  Baghdad  city . The identification of  S. marcescens confirmed by using the systems API 20E and VITEK-2. Also the identification of genus was conducted by detection the specific gene 16S rRNA by   polymerase  chain  reaction (PCR) assay. Twenty eight isolates were found to produce hemolysin as indicated by clear zone around colonies grown on blood agar plates. Four  isolates which  gave highest absorbability  at 405 nm for hemolysin producing  isolate (1.09 A) in standardized conditions (pH 7,37 Cº ,24 hours), while highest absorbability for hemolysin producing isolate which gave  (1.92A) in 48 hours and (1.04A) in 72 houre . It was found that the highest value of gene expression fold was recorded for the gene shlA    in conditions at 48 hours was (7.32) and at 72 hours was (2.64) . It was apparent there was a direct proportion between absorbability for hemolysin  values and folds of gene expression, therefore the changeover conditions growth of bacteria Serratia marcescens leads to changeover of gene expression.  16S rRNA gene expression  results, which was used as reference gene, confirmed that this gene was well suited as housekeeping gene.