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 heat-shock response in Blustocludiellu emrrsonii is dependent on the developmental stage. Cells exposed to elevated temperatures at different stages of the life cycle (sporulation, germination or growth) show a differential synthesis of heat-shock proteins (hsps). Of a total of 22 polypeptides induced, particular subsets of hsps appear in each phase, demonstrating a non-coordinate heat-shock gene expression. In contrast, heat-shock-related proteins (hsp76, hsp70, hsp39a) are spontaneously expressed at a high level during sporulation. By the criteria of two-dimensional gel electrophoresis and partial proteolysis mapping, the 70000-Da protein, whose synthesis is induced spontaneously during sporulation, is indistinguishable from the heat-inducible hsp70. The techniques of in vitro translation, and Northern analysis using a Drosophilu hsp70 probe, demonstrated that enhanced synthesis of hsp70, which occurs during heat-shock treatment and spontaneously during sporulation, is associated with an accumulation of hsp70 mRNA. These observations suggest that hsp70 gene expression is induced during sporulation.The heat-shock response is a typical physiological reaction qf prokaryotic and eukaryotic cells, induced by heat shock and other environmental stresses [I, 21. Certain genes, which are essentially quiescent at normal temperatures, are transiently transcribed and a new set of proteins (heat-shock proteins, hsps) is synthesized; frequently there is an accompanying interruption of normal protein synthesis. Although the pattern of hsps depends on the organism, the cell type, the temperature and the duration of exposure, both the induction mechanism at the transcriptional level and the structure of some of the proteins show a striking degree of conservation. Thus the Drosophilu hsp70 gene hybridizes to genomic sequences from many different organisms [3, 41 and can be induced concomitantly with the heat-shock response in different eukaryotes; heat-shock proteins from a series of eukaryotic organisms are antigenically related [5] and a consensus sequence element was identified in the promotor region of different hsp genes [6, 71. In addition to a transcriptional control, selective translation of the heat-shock mRNAs has been demonstrated in some systems [8 -101.The function of the hsps remains unknown, although the heat-shock response is frequently viewed as a cellular survival function conferring protection against the momentary and subsequent stress to the cell. Besides a role in the response to stress, these proteins may play a role in normal development. This hypothesis is based on the observation that some of the hsps are expressed during oogenesis and pupation in Drosophilu or during the two-cell stage in mouse embryo [II, 121. To understand better the possible role of hsps in differentiation it is important to investigate other developmental systems. An ideal model system is that of the aquatic fungus Blustocludiellu emersonii. This organism undergoes two distinct phases of cell differentiation: germination and ...
The changes in the degree of phosphorylation of ribosomal protein S6 during the life cycle of the aquatic fungus Blastocladiella emersonii were analyzed by two-dimensional gel electrophoresis. Three phosphorylated derivatives of S6 are present throughout the kntire life cycle. However, under certain germination conditions, more highly phosphorylated derivatives of S6 appear. Nonetheless, the resumption of protein synthesis that occurs during germination is not dependent on those highly phosphorylated derivatives of S6.The pattern and sites of phosphorylation of S6 labelled in uivo with [32P]orthophosphate have been compared with those of 40s ribosomal subunit labelled in uitro by partially purified protein kinases. Three major phosphopeptides were found in S6 isolated from the zoospore, while six phosphopeptides were found after zoospore germination (in germling cells). The phosphopeptide patterns of S6 phosphorylated by the CAMP-dependent protein kinase and by casein kinases I and I1 were completely distinct. Only the CAMP-dependent protein kinase gives rise to a phosphopeptide found in 32P-labelled cells, indicating that one of sites phosphorylated in vivo is also phoshorylated in vitro by the CAMP-dependent protein kinase.Protein S6 of the small (40s) ribosomal subunit, the major phosphoprotein of eukaryotic ribosomes, can be phosphorylated at multiple sites (at least five) in viuo [I -41. Although S6 phosphorylation has been observed under different physiological conditions [3], its role is not clear. Correlations have often been observed between an increase in the phosphorylation of protein S6 and elevated levels of protein synthesis [3,4], whereas dephosphorylation is generally associated with decreased protein synthesis [5,6]. However, an increasing number of exceptions to this rule have appeared and phosphorylation of S6 can be stimulated under conditions in which total protein synthesis is either increased, inhibited, or unaltered [3,4,7]. The dephosphorylation of S6 which accompanies the heat-shock response in cultured Drosophila cells also may not be causally associated with either the synthesis of heat-shock proteins or the turn-off of normal protein synthesis that results from heat shock [S]. As demonstrated by Ward et al. [9], increased phosphorylation of S6 does not seem to be universal event in the activation of protein synthesis at fertilization of sea urchin eggs. For hepatocytes and HeLa cells, it has been shown that different agonists lead to significantly different S6-derived phosphopeptide patterns [lo, 111, suggesting that two seperate pathways (CAMPdependent or CAMP-independent) are involved in the process. In quiescent 3T3 cells stimulated with serum, an ordered phosphorylation of S6 was observed and ten major phosphopeptides were found [12].The life cycle of Blastocladiella emersonii is characterized by certain features which make this aquatic fungus an experimentally convenient organism for the study of the (EC 2.7.1.37).significance of S6 phosphorylation. The life cycle consists of a...
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