Diversidade e perfil de resistência de cepas bacterianas heterotróficas isoladas de solo contaminado por rejeito de mandioca

Abstract

The production of cassava (Manihot esculenta Crantz) provides food by-products, such as cassava flour, for example, of great importance for the populations of the Brazilian Amazon. The liquid extracted from cassava pressing for the production of this by-product is called manipueira, which, when discarded irregularly, causes environmental damage due to the high level of toxicity and harmful compounds, such as hydrocyanic acid, negatively impacting the microorganisms present in the soil. The present work was divided into two chapters and aimed to evaluate the diversity and bacterial resistance present in the soil impacted with cassava. The soil used in this research was collected in an area located at the Universidade Federal do Oeste do Pará, Tapajós campus, which has the characteristics of being terra preta, and the place having a smaller flow of people circulating, although the presence of animals is constant. After collection, the soil was stored in two containers with a capacity of 20L, containing holes at its base, where it was poured until it reached the maximum capacity of the container, which were called treatment M1 and M2. It was then subjected to the residue of 5 liters of manipueira, which were poured so that the soil was soaked, and when it reached the bottom, it was filtered through the holes in the container. They were placed in an open place, exposed to the natural conditions of the environment, and the collection period is considered rainy in the region. 25 g samples from each container were collected every 15 days for a period of 45 days, submitted to serial dilution up to 10-5, from which 200 μl were removed and inoculated, in duplicate, in Plate Count Agar (PCA) using the spread plate technique to obtain bacterial growth. Afterwards, the Gram reading was performed for the morphological identification and purity of the isolates, the biochemical identification was performed with the aid of the Bergey key and selection of bacteria based on the resistance profile from the disk diffusion technique, which were submitted to tests for 11 antibiotics distributed between spectrums of action. It was observed in the first chapter that the diversity of bacteria in the M2 treatment prevailed in comparison to the M1 treatment, however through the statistical analysis the results were not significant. There was a prevalence of Gram positive bacteria of the genus Clostridium spp. in both treatments, and in the 4 collection times. It is noteworthy the presence of the genus Staphylococcus aureus only in treatment M1 and Bacillus spp. only in treatment M2. In the second chapter, Gram positive bacteria of the genus Clostridium spp. showed resistance to the antibiotic Oxacillin and Penicillin in the collections, while Gram negative bacteria of the genus Pseudomonas spp, Aeromonas spp. followed by the species Klebsiella peneumonie showed resistance to the antibiotic Ampicillin. The antibiotics with the highest resistance profile belong to the β-lactam class, capable of inhibiting the actions of bacteria that produce β-lactamases. As a result, the bacterial microbiota proved to be tolerant to the harmful compounds of manipueira, although other studies point to a problem regarding the contaminating residue. Resistant strains can be observed in the present work, which reflects on the ability of these bacteria to resist under extreme conditions, such as the case of soil contaminated by manipueira characterized by its toxic compounds.