Folia Microbiol.35, 183-189 (1990) Lytic Effect of Vibrio cholerae Elastase on Gram-Positive and -Negative Bacteria M. KAUR', M. GUFrA a, K.K. TRIPATHI b and K.G. GUPTA* aDepartment of Microbiology, Panjab University, Chandigarh 160 014, India bCentra/Research Institute, Kasanli, India Received December 8, i988 ABSTRACT. Elastase of Vibno cholerae caused the lysis of freshly grown cells of Gram-negative (Pseudomonas aerus/nosa, Proteus vulgaris, Salmonella paratyphi A and Klebsiella pneumon/ae) bacteria. Gram-positive (Staphylococcus aureus and $. ep/derm/d/s) organisms were resistant to this enzyme. Heat killed and lyophilized Gram-positive and -negative bacteria (except $. aureus and S. epidermiclis) showedhigher sensitivityto elastase. Both Gram-negative and -positivebacteria were lyzedmaximally by elastaseat pH 8.0. At this pH, lyticactivity of elastasewas maximum in Tris-HCiand glycine-NaOHbuffersfollowed by Tris-maleate and cacodylatebuffers. Elastases may be defined asenzymes which catalyze the solubilization of elastin through proteolytic cleavage. These enzymes have a preferential affinity for peptides or ester bonds adjacent to nonpolar aliphatic L-amino acids, especially L-alanine (Thomson and Blout 1973). This enzyme was obtained from both eukaryotic and prokaryotic cells. However, pancreatic elastase (EC 3.4.21.36) and leukocyte elastase (EC 3.4.21.37) are well studied. Chemical analogies between the cross-links of some bacterial peptidoglycans and mammalian elastin fiber are known (Janoff et al. 1975). Because of these similarities, the role of mammalian tissue elastase in the clearance of phagocytozed microorganisms, such as M/crococcns roseus and Staphylococcus aureus, has been studied (Janoff and Blondin 1973 ; Janoff et aL 1975). However, the effect of bacterial elastase on bacterial cells requires examina- tion because it might play an important role in the eco-system of mixed populations. Therefore, in the present investigation, the lytic effect of Vibrio cholerae elastase on both Gram-positive and -negative bacteria, was studied.