Isolation and characterisation of Xanthomonas campestris from plant sources

Abstract

A study was conducted to isolate the ease of isolating the bacterium Xanthomonas campestris from plant sources and the cultural characteristics of the isolates. The leaves of eight different plants namely: rice (Oryza sativa), tomatoes (Lycopersicum), beans (Vigna magniculata), sorghum (Sorghum bicolor), pepper (capsicum nnum), soyabeans (Glycine max), cabbage (Brassica oleraceavar. capitata), and mango (Magnifera indica), showing visible symptoms of xanthomonas bacteriosis were obtained from farm fields in Bauchi and screened on glucose nutrient agar (GNA) for Xanthomonas campestris. From the preliminary screening nine bacterial isolates B1, B3, B4, CB1, CB2,CB3, CB4, CB5 and CB6 were selected on the basis of being yellow pigmented and Gram-negative rods. These isolates were physiologically and biochemically characterised by standard determinative procedures. Only isolate B3 obtained from beans (Vigna unguiculata) was identified as Xanthomonas campestris, on the basis of its Gram-negative reaction, yellow pigmentation, mucoid growth on GNA, requirement of oxygen, production of hydrogen sulphide from sodium thiosulphate and peptone, acidification of carbohydrates, lack of urease, motility and abilit to hydrolyse starch, casein and gelatin. Xanthomonas campestris B3 isolated had optimum sodium chloride tolerance of 2% and a maximum of 8%, acid-tolerant (pH 4.5), grows rapidly at 37 degree Centigrade and a relative growth decline at 40 degree Centigrade. xanthomonas campestris B3 can form a good starter culture for the production of xanthan.