Relations between soil attributes and the abundance of Bacillus thurigiensis in the Cerrado of Maranhão state, Brazil

Relações entre atributos do solo e a abundância do Bacillus thurigiensis no Cerrado do estado do Maranhão, Brasil

Abstract

The influence of abiotic factors on the abundance of microorganism populations in soil has been sparsely studied, especially regarding Bacillus thuringiensis (Bt) bacteria. Therefore, this research was aimed at analyzing the relationship between the chemical and textural characteristics of the soil of the Cerrado (savanna) of Maranhão State on the abundance of Bacillus thuringiensis. Soil samples were collected in different municipalities in eastern Maranhão: São Mateus do Maranhão, Alto Alegre, Coroatá, Timbiras and Codó. The soil samples were obtained in the 0-0.1 m layer for soil fertility and texture analysis. Then, in the same area for the isolation of Bt, 1 g of soil was collected. The colonies obtained in the isolation that featured morphological characteristics of Bacillus spp. were visualized under phase contrast microscopy. Principal component analysis, clustering and correlations were peformed. Results: The sand content correlated positively with the Bacillus thuringiensis index (iBt). The cluster analysis allowed for verifying that the soils not showed iBt in function of high concentrations of aluminum (Al) and potential acidity (H+Al). Considering as these attributes (Al and H+Al) alter the availability of P in the soil, the abundance of Bacillus thuringiensis may have been impaired by the deficiency of this element in the environment. Conclusion: Bt has correlations with soil texture, and high concentrations of aluminum and potential acidity in the soil influencing the permanence of Bacillus thuringiensis in Maranhão eastern Cerrado.

Keywords:
bacteria; soil fertility; acidity