Morphological characterization of soil bacteria in Ngere tea catchment area of Murang'a County, Kenya

Abstract

Bacteria are a very diverse group of organisms in soil, and major taxonomic groups are represented in most soils. The extent of the diversity of microorganisms in soil is seen to be critical to the maintenance of soil health and quality, since a wide range of bacteria are involved in the important soil functions. The objectives of this study were to isolate, characterise morphologically bacteria that are associated with soil quality in tea growing areas of Ngere. Thirty eight isolates were obtained using two categories of media, namely dilute nutrient broth agar and Tryptone soy agar. Ngere tea soils had a pH range of 3.9 to 5.0 and organic carbon content that ranged from 3% to 19%. The isolates were characterized using cultural and biochemical techniques. The Gram stain reaction showed that 53% of the isolates were Gram positive while 47% were Gram negative, and they grew well at pH ranging from 5 6.5 and temperature range of 25oC to 35oC This study demonstrated that Ngere tea soils harbours diverse bacteria with specific biochemical properties like the ability to reduce nitrate to nitrite, nitrogen fixation, ability to produce urease enzyme that splits urea into carbon dioxide and ammonia, ability to hydrolyse starch and to solubilisation phosphate suggests their involvement in the nutrient recycling within the tea soils hence improving soil fertility. The presence of isolates such as D5, D16, S31, D2, and S23 could indicate that they can be used both as bio control agents for weeds. Furthermore, presence of isolates: D61, D19, S30, D1, D78, D13, S55, D60, D79, S48 among others and high percentage of organic carbon content, strongly suggested extend of fertility of this soils because this isolates are important element in mineral recycling hence can be used as indicators of soil health\ biosensors or biofertilizers.