Atividade e população microbiana envolvida nas transformações do enxofre em solos com diferentes vegetações

Abstract

Resumo -O objetivo deste trabalho foi determinar as populações microbianas e suas atividades envolvidas no ciclo do S, de solos virgem e cultivado, e as suas relações com as diferentes frações de S no solo. Das populações de microrganismos pesquisados, apenas foram encontradas as bactérias autótrofas oxidantes de S 0 em pH 5,0 e as heterótrofas oxidantes de tiossulfato, que representaram menos de 0,1% das bactérias totais. A média das bactérias autótrofas foi o dobro das heterótrofas. As maiores contagens de bactérias totais, autótrofas e heterótrofas foram encontradas nos solos com milho, de pastagem e de floresta integrada, respectivamente. A atividade da arilsulfatase foi maior em solo de floresta integrada e a da rodanase em solo de pastagem. A arilsulfatase correlacionou com as populações de heterotróficos, C orgânico, S total, S orgânico, matéria orgânica e umidade do solo; e a rodanase com C orgânico, S total e S orgânico. Os teores de S orgânico e sulfato foram de 94-98% e 2-6% do S total, respectivamente. Os maiores teores de S total e orgânico foram encontrados no solo de floresta integrada. O S total correlacionou com o S orgânico, umidade e matéria orgânica, e o S orgânico com a matéria orgânica.Termos para indexação: bactéria, oxidação, arilsulfatase, rodanase. Activity and microbial populations involved in sulfur cycling in soils with different vegetationsAbstract -The objective of this work was to assess the microbial populations and its activities involved in the S cycle, of virgin and cultivated soils, and its relationships with the different fractions of S in the soil. The influence of soils with different vegetations on microbiological and biochemical characteristics was investigated. Out of the different populations of microorganisms examined, only the S 0 -oxidizing autotrophic bacteria and thiosulfate-oxidizing heterotrophs that represented less than 0.1% of the total bacteria were found. The average of autotrophs was double that of the heterotrophs. The highest counts of total bacteria, autotrophic and heterotrophic microorganisms were found in corn, pasture and forest soils, respectively. Arylsulfatase activity was greater in forest soil, and rhodanese activity in pasture soil. Arylsulfatase correlated with heterotrophic populations, organic C, total S, organic S, organic matter and soil moisture; and rhodanese with organic C, total S, and organic S. The contents of organic S and sulfate were of 94-98% and 2-6% of total S, respectively. The major content of total S and organic S was found in the forest soil. Total S correlated significantly with organic S, moisture and organic matter and organic S with organic matter.Index terms: bacteria, oxidation, arylsulfatase, rhodanese. IntroduçãoO S é um dos elementos mais abundantes na terra após o C e o nitrogênio. É essencial para os organismos vivos, por fazer parte da constituição de proteínas e outros compostos orgânicos, e por ser fonte de energia para as bactérias litotróficas e aceptor de elétrons oriundos do metabolismo respiratório das ...

Comparison of microbial numbers in soils by using various culture media and temperatures

“…Nevertheless, both groups of microorganisms were affected by plant type (Buyer et al, 2002). Similar reports have shown that the size and structure of microbial populations are affected by soil type and plant species (Wieland et al, 2001;Pinto and Nahas, 2002). However, a study made on three soils in England, showed that the primary determinant of composition in bacterial communities was the soil type (Girvan et al, 2003).…”

“…The type of soil was considered a determinant factor in the composition of microbial populations in cultivable soils (Damastri et al, 1999;Girvan et al, 2003). However, other authors (Miethling et al, 2000;Pinto and Nahas, 2002;Sanomiya and Nahas, 2003) have shown that in the same soil type different plant species influence microbial populations distribution.…”

Bacterial diversity of soil under eucalyptus assessed by 16S rDNA sequencing analysis

“…Most studies on eucalyptus focus on the impact this tree has on the chemical properties of the soil, nutrient content, ions exchange capacity and microbial activity (Lima, 1996), as an example microorganisms involved in sulfur transformations (Pinto & Nahas, 2002) and natural phosphates solubilization (Silva Filho et al, 2002). Several papers describe major impacts of the use of this monoculture on the microbial communities (Lima, 1996) as well as the possibility of ecological changes on soils cultivated under eucalyptus (Fonseca, 1984).…”