Studies on the diversity, abundance and succession of hydrocarbon utilizing micro organisms in tropical soil polluted with oily sludge

A research was carried out in a tropical region to study the population of hydrocarbon utilizers in soil polluted with oily sludge. Plots were prepared to receive treatments with neat and emulsified oilysludge. These plots were further treated with fertilizer and bioaugmented with a consortium of hydrocarbon utilizers for six months. Results obtained indicated that, the presence of oily sludge in soilcaused the growth of diverse genera of oil degraders. The major genera of bacteria active in polluted soil were Pseudomonas, Bacillus and Acinetobacter, while fungal general were Aspergillus, Penicillium,and Mucor. Abundant microbial growth was observed during the first 60 days. Some organisms such as Pseudomonas, Bacillus, Penicillium, and Aspergillus were present in polluted soil throughout the experimental period, while others including Candida, Sporobolomyces and Rhizopus were found only during the first two months. Further analysis revealed that, succession of the hydrocarbon utilizers in polluted soil was subject to seasonal variations and depended primarily on the fraction of the oil being utilized at a specific time and also on the physiology of the micro organisms involved. In addition, the selective appearance and succession of hydrocarbon utilizers in the polluted soil were affected only by the presence of neat and emulsified oil in soil as compare to other treatment parameters. The practical implication of these findings suggests that reloading of oil in some treated plots could be carried outafter the first 90 days. Molecular techniques are underway to provide a more comprehensive study on this successional trend

Metal Distribution and Bioaccumulation in Water and Fish of a Tropical Lake

A study was conducted to investigate the metal (copper, zinc and manganese) concentrations in the surface water and fish of a man-made lake receiving agricultural and domestic effluents in Ibadan, Nigeria. The lake (Main Lake, IITA) is a site of drinking water abstraction and the major water source for the surrounding agricultural research farms. Factor analysis indicated that copper was an important contributor to the total variance observed in the lake, being involved in Factor 1 of the 6-factor model. Significant differences occurred in the copper and manganese levels of the organs of Oreochromis niloticus at P< 0.05 and P< 0.01 respectively and in manganese levels of Sarotherodon. galilaeus at P< 0.05. Significant differences did not occur in Lates niloticus and Synodontis nigrita organs. Bioaccumulation factors from water to fish muscles were highest for manganese ranging from 4.56-10.56; zinc from 1.83-5.67 and copper from 1-1.8. These factors showed that despite the low levels of these metals in surface water, there may be an onset of bioaccumulation in some of the fishes. This work contributes to the baseline data on the presence and effects of metals in African freshwaters and could aid future plans for the control of toxic build-up in our aquatic environments. Keywords: Metal, concentrations, lake, bioaccumulation, water, fish and IITATropical Freshwater Biology Vol. 17 (1) 2008: pp. 81-9

Biological control of cacao diseases

This chapter discusses the advances in biological control of cacao diseases over the last 15 years. Most attention has been focused on biological control of frosty pod rot (Moniliophthora roreri), witches' broom (Moniliophthora perniciosa) and black pod disease (Phytophthora spp.). Research on biocontrol of other diseases in the cacao phyllosphere or rhizosphere is scarce or in its infancy. There is, however, a steady increase in information regarding the factors influencing and the mechanisms underlying biological control of cacao diseases as well as practical aspects such as inoculum production, formulation and application. There has been a clear shift away from inundative approaches using epiphytic BCAs towards more classical biocontrol approaches using bacterial and fungal endophytes as well as vesicular arbuscular mycorrhiza. These have the advantage that they can permanently establish themselves in the cacao tree. Moreover, besides direct competition for space and nutrients, antibiosis and mycoparasitism, through induced resistance and growth promotion, endophytes have a larger arsenal of mechanisms through which they can help protect their host. Endophytic BCAs could thus provide more effective and sustainable disease control. Recent advances in our understanding of the mechanisms through which endophytic biocontrol agents can reduce pest and disease impact provide possibilities for innovative disease control strategies, including combination therapies together with natural or chemical products. Continued work on production, formulation and application is also necessary in order for biocontrol to become economically interesting. However, biological control will not become a stand-alone solution for disease control but should become part of integrated pest management strategies, with cultural management as a central and reinforcing pillar. (Résumé d'auteur