MOLECULAR AND CULTURE-BASED ANALYSES 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 important soil functions.The objectives of this study were to isolate, characterise and identify groups of 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 the pH range of 3.9 to 5.0 and organic carbon content ranged from 3% to 19%. The isolates were characterized using cultural and biochemical techniques. The Gram staining 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. Identification was done by Polymerase Chain Reaction (PCR) amplification of the 16S rDNA region, sequencing and phylogenetic analysis. Analysis of partial sequences using Blast showed that 56% were from the genus Bacillus with similarities between 92% and 100%, 18% belonged to the genus Pseudomonas with similarities of 99%. Other genera such Burkholderia, Chryseobacteriumand Acinetobacter constituted 26% with similarity between 91% and 99%. Based on this study, the presence of isolates such as D5, D16, S31, D2, and S23 and could indicate that they can be used bothas bio control agents for weeds and biopesticides since they have the ability to produce bioactive compounds which can be used as replacements for synthetic pesticides that are active against fungal pathogens such as root rot fungi which frequently affects tea roots. 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 the 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.