A small rod, capable of forming crater-like plaques on lawns of Vibrio parahaemolvticus, was isolated from a marine environment.The isolate was a gram-negative straight rod with round ends and was small in size, equal to 'that of halophilic Bdellovibrio strain 5501. The isolate appeared to have close taxonomic relationships to Cytophaga, since this bacterium moved slowly in a gliding manner on a solid agar surface, hydrolyzed agar and starch, contained yellow pigment and was halophilic. The isolate was able to grow not only under host-dependent but also under host-independent conditions when low nutrient media were used for cultivation, and its bacteriolytic mode was different from that of Bdellovibrio, an endoparasite. The isolate was halophilic and required Mg++ and Ca++ in addition to 3% saline for growth. The isolate showed a broad host range when tested for plaque-forming activity on gram-negative bacteria but not on the gram-positive bacteria tested so far.A considerable number of bacteria, parasitic or predatory against other microorganisms, have been isolated from various natural environments. Bdellovibrio, a unique endoparasite, has been physiologically and morphologically investigated in detail by many workers. Myxobacteria are widely recognized for their capacity to lyze other bacteria [1,3,5]. Shilo isolated from fish ponds a gliding bacterium, myxobacter FP-1, capable of lyzing many species of blue green algae as well as certain bacteria [14]. Stewart and Brown reported a similar gliding bacterium, Cytophaga N-5 [15]. However, little information on predatory bacteria has been obtained from marine environments [9,11,13].In the course of experiments on the distribution of halophilic Bdellovibrio in marine environments, crater-like plaques were detected on a lawn of Vibrio parahaemolyticus.A small rod, exhibiting gliding motility, was isolated as the lytic factor.The isolation and characterization of the small rod, which has been herein referred to as gliding bacterium strain MC-3 (MC-3), are described in this paper.
MATERIALS AND METHODSOrganism. The host organism used in this work was Vibrio parahaemolyticus A55 unless otherwise stated. The organisms used in studying the activity spectrum of the isolate were V. parahaemolyticus, Vibrio alginolyticus 73-59-la, Vibrio costicola NCMB 701, Vibrio anguillarum NCMB 829, Escherichia coli UKT, Salmonella typhimurium 4006, Bacillus subtilis NRRLB 558, Staphylococcus aureus # 100 and Clostridium perfringens NCTC 8239. The V. parahaemolyticus strains were nine pilot strains of 0 antigen obtained from the National Institute of Health, Japan.V. alginolyticus 73-59-la and S. typhimurium 4006 were isolated in this Laboratory.V. costicola NCMB 829, E. coli UKT and B. subtilis NRRLB 558 were obtained from the Laboratory for Culture Collections,
