Isolation and Characterization of Bacteria Involved in Daniellia oliveri, Ficus sycomorus, Hymenocardia acida andTerminalia glaucescens Leaf Litter Decomposition and their Hydrolytic Enzyme Potentials

Abstract

The effect of microorganisms particularly those of bacteria on litter decomposition in the tropical savannahs of Adamawa Cameroon is poorly investigated. Litter decomposition was conducted in the field on the litter of Ficus sycomorus, Terminalia glaucescens, Daniellia oliveri, and Hymenocardia acida, and the dynamic of bacterial populationas well as their enzymatic activity during degradation of leaf litters was studied. For this purpose, bacteria were isolated from the litterof these plants at the initial time (zero), 12 and 24 weeks of degradation by serial dilution method and spreading onto nutrient agar culture medium. Identification of bacteria was done under photonic microscope after Gram staining and the production of enzymes was carried out on specific media. Results indicate that: 25 bacteria were isolated from distinct phenotypic characteristics on nutrient agar. Based on morphological appearance as observed under light microscope, 24% of isolates were found to be single bacilli; 28% bacilli cluster; 16% were found to be streptobacilli and 32% diplococci. For sugar fermentation test (TSI), 20% of isolates produced gas and acidic reaction, 40% produced acidic butt reaction, while only 20% produced H2S gas ; 76% of isolates were positive to citrate utilization (SIM) test; 20% of isolates were positive to catalase production test, whereas only 20% of isolates were motile. The aforementioned study of phenotypic, microscopic and biochemical enabled identification of two genera: the genus Bacillus and the genus Micrococcus representing respectively 68 and 32% of the isolates. The genus Bacillus consisted of Bacillus cereus (41.17%, with 7 phenotypes), Bacillus megaterium (17.64%, with 3 phenotypes), Bacillus subtilus (35.29%, with 6 phenotypes) and Bacillus sp. (5.88%, with 1 phenotype). The genus Micrococcusre grouped 08 phenotypes. The relative abundance of isolates demonstrated that in all leaf litters and soils, there was a great diversity of bacterial isolates at the initial time and then a considerable decrease in this diversity during litters degradation. The genus Bacillus was generally dominant at all decomposition periods of different plant species. A total of 64% of bacteria isolates produced at least one enzyme. 36% of the isolates produced amylase, 56% produced cellulase, 40% produced esterase, 48% produced lipase, while 48 % of the isolates produced protease. This strong enzymatic activity of the isolated bacteria suggests their competences in the degradation process of leaf litter, and therefore, the interest in exploiting them in litter degradation units for an efficient production of organic fertilizer.