Chemotaxis of Bdellovibrio bacteriovorus toward pure compounds

Positive chemotaxis by Bdellovibrio bacteriovorus strain UKi2 was measured for 139 compounds. Twenty-one compounds were attractants; sensitive attraction was elicited by acetate, propionate, thioacetate, malonate, cis-oxalacetate, D-glucose-6-phosphate, acetyl coenzyme A, ammonium ion, barium ion, manganous ion, and potassium ion. Several of the attractants for B. bacteriovorus strain UKi2 also were attractants to strains 6-5-S and 114; however, strains 109D and 109J were not attracted by the compounds tested. Of 33 compounds tested, 8 were repellents for B. bacteriovorus strain UKi2: n-caproate, alanine, isoleucine, leucine, phenylalanine, tyrosine, cobaltous chloride, and hydronium ion. None of the organic repellents for strain UKi2 elicited repulson from strains 114 or 109D. However, all three strains of Bdellovibrio show aerotaxis. Several compounds were tested for their effects on viability and predacious growth of B. bacteriovorus strain UKi2. No simple correlation was found between attraction or repulsion and benefit or harm to bdellovibrios. The data are consistent with the view that in nature, the greatest survival value of chemotaxis for bdellovibros may be in aerotaxis, attraction to certain inorganic ions and acetate, and repulsion by hydronium ion.