Isolation and Characterization of Rheinheimera Sp. from Black Tiger Shrimp Penaeus Monodon

Two bacterial strains designated C9 and C11 were isolated and characterized from black tiger shrimp Penaeus monodon maintained in laboratory conditions. The shrimp exhibited tiny white spots along with clinical signs of bacterial infection, probably, due to suboptimal water quality and resulting stress. Absence of white spot syndrome virus was confirmed by PCR. Bacterial isolates obtained from the haemolymph, hepatopancreas and gills were predominated by two types of strains. Strains C9 and C11 were Gram negative, aerobic, nonpathogenic, pigmented, rod shaped and motile. C9 was highly pigmented whereas C11 was less pigmented. Optimum growth temperature for C9 and C11 was 25 0 C. Lower salinity was more suitable for growth and pigmentproduction. On the basis of the 16SrRNA gene sequence, the strains C9 and C11 were allotted the accession numbers KR135116 and KR135117, respectively. Strains C9and C11 exhibited no differences in their 16S rRNAsequences. They were shown to belong to the class Gammaproteobacteria, being most closely related to Rheinheimera aquimaris with 87% bootstrap support. The DNA G+C content of the two strains C9 (53.36mol%) and C11 (53.14mol%) are the highest reported so far among Rheinmeinhera spp. Molecular data demonstrated that both the strains showed 96% bootstrap support witheach other butdifference in their phenotypic characteristics strongly support that they belong to different biotypes.