Diversity of Heterotrophic Bacteria Isolated from Water in the Paddy Rice Fields of Southern Brazilian

Abstract

This study evaluated the effects of physic-chemical variables on the diversity of bacterial communities present in the water utilized to irrigate rice field and in the water drained back into the water source. The samples were collected between the months of October and April of the year 2009/2010 in three rice producing areas in the district of <i>Caraá</i>, <i>Campo Bom</i> and <i>Esteio</i>, all located in the Basin of the <i>Rio dos Sinos.</i> The data was analysed utilizing Multivariate Analyses (CCA and DCA), Jaccard Distance and Variance Analyses. The abundance of the bacterial colonies was greater in the irrigation water than in that within the rice field or in the drainage. (F1, 9 = 7.21 p < 0.05); 48.6% were found in the irrigation channel, 25.7% in the water within the field and 25.7% in the water returned to the river (drainage). Colonies of 21 species were registered and of these: 16 were in the irrigation channels; the water in the rice field and the drainage water. The estimated diversity was superior in the irrigation channels (H=2.68) when compared with the values obtained in the drainage water (H=2.25). The results demonstrated that the samples from the irrigation water and the drainage water differ in the composition of the species in all the locations analysed. The two initial axes generated by Detrended Correspondence Analysis explain 56% of the observed variation between the locations. The most important variables for the ordination and correlation with the axis were the pH and Nitrogen. The results show that rice bacteria communities contain several species but few are abundant, such as species of <i>Bacillus</i>, <i>Lactobacillus </i>and <i>Pseudomonas</i>. The reduction in colony abundance on the drainage water shows the ability of the rice field to filter some bacterial species.