No abstract

The H2(18O) enrichment, delta, in the water of leaves from four Brazilian trees, was studied. In all trees the leaf water showed a periodic variation in delta, with a maximum in the early afternoon and a minimum around 6 a.m. In general delta was found to be either higher or lower than the stationary enrichment which is supposed to depend only on the relative atmospheric humidity. This effect is due to the slow response of the system to variations of the humidity. For a special case, where steady-state conditions could be anticipated, the kinetic enrichment was obtained to 20 +/- 3%, which agrees with theoretical predictions.

In this investigation, a sugarcane agroecosystem at a coastal tableland, in the northeast of Brazil, was screened to obtain bacteria strains able to synthesize poly-β-hydroxyalkanoates (PHA), using sucrose as the main carbon source. The potential to synthesize PHA was tested qualitatively by Sudan Black staining of colonies growing in different carbon sources: sucrose, glucose, fructose, propionate and cellulose. In a typical sugarcane crop management system, the plantation is burned before harvesting and vinasse, a by-product of alcohol production, is used in a fertirrigation system causing, probably, selective pressures on the microbiota of natural environments. Eighty-two bacteria strains, belonging to 16 different genera and 35 different species, were isolated. The data showed that 11 strains (ca 13%), nine of which belonging to the genus Pseudomonas, presented a strong Sudan Black staining in several carbon sources tested and, simultaneously, showed multiple resistance to antibiotics. Resistance to antibiotics is an advantageous feature for the biotechnological production of PHAs. The total number of isolates with multiple resistance to antibiotics was 73, and 38% of them belong to the genus Pseudomonas. Among the isolates, ca 86% and 43% grew in the presence of 10-100 U/ml of penicillin and/or 100-300 mg/ml of virginiamycin, respectively. These antibiotics are utilized in the alcohol distillery we investigated. The results suggest that some agroecosystem environments could be considered as habitats where bacteria are submitted to nutritional unbalanced conditions, resulting in strains with potential ability to produce PHAs, and also, to an increase in the microbial diversity.

The productivity of a pasture soil (caatinga) located in the region of São João do Cariri, PB, Brazil was evaluated based an the following microbiological parameters: biomass (measured by fumigation-incubation method), activity (estimated from basal respiration and cellulose decomposition rate), qCO2, and Cmic : Corg ratio. This analysis demonstrated that livestock management in the ‘caatinga’ is probably causing environment damage by affecting the soil properties, reducing the microbial biomass and soil respiration and increasing the qCO2, affecting the recovery of this ecosystem.

Mass spectrometric analysis were made while working as a guest scientist at the Institute of Chemistry 2, KFA J/Jlich (Drs. K. Wagener, Director, and H. Foerstel, head of the 180 working group) Add under acknowledgements: The authors gratefully acknowledge logistic and financial support by the KFA Jfilich.