Advances in Microbiology, 2012, 2, 72-78 http://dx.doi.org/10.4236/aim.2012.22009 Published Online June 2012 (http://www.SciRP.org/journal/aim) Molecular Assessment of 16S-23S rDNA Internal Transcribed Spacer Length Polymorphism of Aeromonas hydrophila Vijai Singh 1,2* , Indra Mani 2,3 , Dharmendra Kumar Chaudhary 2 1 Programme d’Epigenomique, Institute of Systems and Synthetic Biology Genopole, French National Center for Scientific Research (CNRS), Evry, France 2 National Bureau of Fish Genetic Resources, Lucknow, India 3 Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi, India Email: * vijaisingh15@gmail.com Received January 20, 2012; revised February 8, 2012; accepted March 12, 2012 ABSTRACT Aeromonas hydrophila is an important bacterial pathogen which causes the hemorrhagic septicemia in fishes, amphibi- ans and humans. Genetic relationships of diverse isolates of A. hydrophila were recovered from fish and water sources. These isolates were investigated by flanked region of 16S and 23S Ribosomal DNA (rDNA) internal transcribed spacer (ITS). Here we analyzed polymorphism of PCR-amplified 16S-23S rDNA ITS and their revealed band pattern consist- ing of one to four DNA fragments. The fragment size ranged from 500 to 1000 bp. The DNA band patterns revealed a considerable genetic diversity in interaspecies. The 750 bp size of band was common in all isolates of A. hydrophila except one Isolates AH21. The tRNA-Glu sequences were identified from 750 bp size of ITS region that could be used as strain level potential genotypic markers. Keywords: Aeromonas hydrophila; Diseases; ITS; tRNA-Glu; Molecular Marker 1. Introduction An epidemic of Aeromonas hydrophila infection with a high rate of mortality (95%) in turtles (Pseudemis scripta) has been reported in Italy [1]. The disease source due to A. hydrophila has caused extensive losses among cul- tured fresh water fishes in mainland China [2,3]. Infec- tion of A. hydrophila occurs in all developmental stages of fish. Several important virulence factors are involved in the pathogenesis, which reduce the immunity and thereby damage cellular activity in fish that allows the susceptibility to disease outbreaks and high rate of mor- tality. Aeromonas has been isolated from diarrheic chil- dren, fish, milk and ice creams; and 57% isolates pro- duced the enterotoxin [4]. Moreover A. hydrophila has also been isolated from blood and bilious fluid of women with liver cirrhosis [5]. A. hydrophila causes several dis- eases in humans like diarrhea, soft tissue infections, meningitis, endocarditis, peritonitis, hemolytic-uremic syndrome and septicemia in immunocompromised [6]. A. hydrophila is a significant bacterial pathogen of a wide variety of hosts, which is associated with hemor- rhagic septicemia in fishes, reptiles and amphibians [7]. In fishes, they cause well known diseases like hemor- rhagic septicemia, fin as well as tail rot and result in the high mortality in commercial aquaculture system [8]. Freshwater reservoirs are decreasing due to growing po- pulations, increased human consumption, urbanization and the lack of cost-effective sewage water treatment systems [9,10]. Several species of Aeromonas isolates were recovered from cultured fish and was characterized by biochemical as well as 16S rDNA sequences. The pathogenicity assay has been performed in healthy fishes and found pathogenic bacteria such as A. hydrophila, A. bestiarum, A. salmonicida and A. veronii. All these Ae- romonas isolates were isolated from diseased trout ex- cept one which from carp fry [11]. Therefore, it is urgent need to well characterize by molecular tools to discrimi- nate pathogenic and non pathogenic isolates of A. hy- drophila. Since last decade, several molecular techniques have been developed for characterization of bacteria. The study of non-coding RNAs is important in searching the function or role in cells. In order to understand the func- tion, we may find the secondary structure. The family of tRNAs is a type of RNA molecules which has particular function to translate amino acids into protein-building * Corresponding author. Copyright © 2012 SciRes. AiM