Journal of Environmental Biology

Effect of pH and salinity on pathogenicity of Flavobacterium columnare

and Myxobacterium sp. in Indian cat fish, Clarias batrachus (Linn.)

and Heteropneustes fossilis (Bloch.)

Author Details

Vinay Verma

Aquatic Biotechnology and Fish Pathology Laboratory, Department of Animal Science, M.J.P.

Rohilkhand University, Bareilly - 243 006, India

Yogendra Prasad

(Corresponding author)

Aquatic Biotechnology and Fish Pathology Laboratory, Department of Animal Science, M.J.P.

Rohilkhand University, Bareilly - 243 006, India

e-mail: yogendraps_2004@yahoo.co.in

Bhoj Raj Singh

Division of Bacteriology and Mycology, Indian Veteninary Research Institute, Izatnagar - 243 122,

India

Publication Data

Paper received:

29 February 2009

Revised received:

07 November 2009

Re-revised received:

07 April 2010

Re-re-revised received:

29 August 2010

Accepted:

24 September 2010

Abstract

Flavobacterium columnare (FC) and Myxobacterium sp. recorded persistently associated in fish hatchery and culture system of Himalayan and Sub - Himalayan regions were found to be pathogenic.? The pH and salinity played a significant role on the pathogenicity of these potent pathogens in case of Clarias batrachus and Heteropneustes fossilis. LD₅₀ value of FC was 10^4.5 CFU in both the fishes and those of Myxobacterium sp it was 10⁶ CFU ml^-1 fish^-1.? Fish challenged with F. columnare and Myxobacterium sp. (@ 0.2 ml fish^-1) individually consisting 10⁵-⁶cfu ml^-1 exhibited explicit symptoms of columnaris disease and marked with ulceration and saddle back lesion on the dorsal side of body. Maximum reisolation of inoculated bacteria was recorded at pH 7.0 and 7.5 and at 0.0-0.5 (F. columnare) and 0.0-1.0% (Myxobacterium sp.) salinity. Foregoing results elucidated that F. columnare was more sensitive to salinity in comparison to Myxobacterium sp. and their pathogenicity significantly (p<0.05) depends on the salinity and pH that might be one of the physical factors to control their proliferation.

Key words

Catfish culture, Columnaris disease, F. columnare, Myxobacterium

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