Quantificação de bactérias totais e esporuladas no solo

Abstract

RESUMO: Este trabalho analisou o efeito da temperatura e período de incubação e da diluição do inóculo, em dois meios de cultura, sobre a quantificação de bactérias totais e esporuladas. O crescimento quantitativo e qualitativo de bactérias totais e esporuladas depende tanto do meio de cultura, temperatura, diluição e tempo utilizados como da interação desses fatores. O meio de TSA apresentou maior contagem que o meio de Thorton de unidades formadoras de colônias (UFC) de bactérias totais mas não de Bacillus spp. As colônias crescidas no meio de TSA apresentaram maior tamanho e forma mais nítida. O cultivo à temperatura de 30°C propiciou maior número de UFC que a 25°C, sobretudo nos primeiros dias de incubação. O crescimento bacteriano correspondeu a uma equação de 3 o grau. Dependendo do meio de cultura, da temperatura de incubação e da diluição, os períodos de máximo crescimento foram de 4,9 a 6,9 dias para as bactérias totais e de 4,4 a 7,2 dias para Bacillus spp. Embora tenham sido utilizadas diluições decimais dos inóculos, as proporções entre as contagens variaram de 6,3 a 10,0 vezes para as bactérias totais e de 2,0 a 7,0 para as esporuladas. Palavras-chave: Bacillus spp., bactérias totais, solo QUANTIFICATION OF TOTAL AND SPORULATING BACTERIA IN SOILSABSTRACT: This work studied the effect of the temperature and incubation time and of the inoculum dilution, in two culture media, on the quantification of total and sporulating bacteria. The quantitative and qualitative growth of total and sporulating bacteria depended on the growth medium, temperature, dilution and incubation time, as well as on the interaction of these factors. Tryptic Soil Agar medium presented a greater number of colony forming units (CFU) for total bacteria. However, for Bacillus spp. there were higher counts on Thorton medium. Colonies grown on Tryptic Soy Agar medium were of larger size and had a more clearly defined shape. An incubation temperature of 30 o C yielded more CFU than incubation at 25 o C, especially during the first days of incubation. Bacterial growth was fit to a mathematical model and corresponded to a third degree equation. Depending on the growth culture medium, incubation temperature and dilution, periods of maximum growth were between 4.9 and 6.9 days for total bacteria and between 4.4 and 7.2 days for Bacillus spp. Although decimal inoculum dilutions were used, proportions between counts based on different conditions ranged from 6.3 to 10.0 times for total bacteria and from 2.0 to 7.0 times for sporulating bacteria.

Methods to quantify Bacillus simplex-based inoculant and its effect as a seed treatment on field-grown corn and soybean in Brazil

“…Method 3 recovered a smaller number of colonies but the colonies were larger than the ones observed in the other two methods. Vieira and Nahas (2000) found similar results when evaluating Bacillus spp. isolates from soil samples.…”

Biodegradation of Organophosphorus Compounds Predicted by Enzymatic Process Using Molecular Modelling and Observed in Soil Samples Through Analytical Techniques and Microbiological Analysis: A Comparison

“…From each serial dilution, 0.1 mL aliquots were removed and spread with a Digralski spatula on tryptic soy agar (TSA) culture medium plate surface autoclaved at 121 • C for 30 min and cooled prior to use. This media was chosen because in the test performed by Vieira and Nahas [45], for quantification of total bacteria in soil samples, it presented the best results. This procedure was replicated three times in different plates.…”

Avaliação Da Microbiota Bacteriana Presente Na Região Da Restinga De Jurubatiba Após Simulação De Derrame De Petróleo

“…Posteriormente às diluições foram inoculados 100µl em duplicata em placas com meio de cultura para heterotróficos totais contendo extrato de carne 3 -5 g/L; peptona 10 g/L; NaCl 5 g/L; ágar bacteriológico 25 g/L a pH 7,0 (Li et al, 2000). As placas foram incubadas em estufa a 30º C e a contagem das colônias foi realizada após 48 h de crescimento com o auxílio de um contador de colônias (Vieira & Nahas, 2000).…”