Culturable populations of Acinetobacter can promptly respond to contamination by alkanes in mangrove sediments.

This study evaluated the potential of bacterial isolates from mangrove sediments to degrade hexadecane, an paraffin hydrocarbon that is a large constituent of diesel and automobile lubricants. From a total of 18 oil-degrading isolates obtained by an enrichment technique, four isolates showed a great potential to degrade hexadecane. The strain MSIC01, which was identified by 16S rRNA gene sequencing as Acinetobacter sp., showed the best performance in degrading this hydrocarbon, being capable of completely degrading 1% (v/v) hexadecane within 48 h without releasing biosurfactants. Its hydrophobic surface probably justifies its potential to degrade high concentrations of hexadecane. Thus, the sediments from the studied mangrove harbour bacterial communities that are able to use oil as a carbon source, which is a particularly interesting feature due to the risk of oil spills in coastal areas. Moreover, Acinetobacter sp. MSIC01 emerged as a promising candidate for applications in bioremediation of contaminated mangrove sediments.

Sulfated chitosan as tear substitute with no antimicrobial activity.

Chitosan of high molar mass and with 82% deacetylation was sulfated using two procedures and characterized. In the first method sample chitosan-S1 was produced using chlorosulfonic acid as the sulfating agent and N,N-dimethylformamide as the medium, and in the second method (chitosan-S2) formic acid was also used. The degrees of sulfation were 0.87 (chitosan-S1) and 0.67 (chitosan-S2). FTIR spectra showed bands at 1230, 800 and 580 cm(-1), attributed to sulfation. Moisture content followed the order: chitosan-S-0.87>chitosan-S-0.67>chitosan. Chain depolymerization was verified by GPC. Aqueous solutions showed pseudoplastic behavior and the viscosity at a concentration of 0.3% (w/v) was higher than that of healthy human tears (close to 3 mPas at shear rate 130 s(-1)). Substitutions in the C2NH and in C6OH groups were verified by NMR. Antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa was not observed. Considering that chitosan-S-0.67 had a higher solubility, less chain depolymerization, higher yield and better thermal stability in comparison with chitosan-S-0.87, the derivative with DS 0.67 offered the greatest potential for use in formulations of tear substitutes.

Cytotoxic activity of fungal strains isolated from the ascidian Eudistoma vannamei.

The cytotoxic activity at 50 µg/ml of extracts obtained from eleven fungal strains associated to Eudistoma vannamei, an endemic ascidian from Northeast Brazil, against two cell lines, i.e., the HCT-8 (colon cancer) and the MDA-MB-435 (melanoma) cell lines, was investigated. The most promising extract (EV10) was obtained from a fungus identified as Aspergillus sp. by molecular analysis and was selected for bioassay-guided isolation of its active principals. Large-scale fermentation of EV10 in potato-dextrose broth followed by chromatographic purification of the active extract from the liquid medium allowed the isolation of the isocoumarins mellein, cis-4-hydroxymellein, and trans-4-hydroxymellein, besides penicillic acid. All isolated compounds were tested for their cytotoxicity against the tumor cell lines MDA-MB-435 and HCT-8 and revealed penicillic acid as the only cytotoxic compound (cell growth inhibitions >95%).

Diversity of a chlorine-resistant Bacillus population isolated from a wastewater treatment station.

This paper describes the phenotypic and genotypic diversity of a Gram-positive, aerobic bacterial population isolated from the chlorine tank of a wastewater treatment plant. A total of 12 sporeforming, rod-shaped isolates were identified using 16S rRNA gene sequencing and biochemical tests. Pairwise genetic comparisons revealed the identity among sequences obtained from isolates varied from 92.6 to 100%. Similarity searches on GenBank showed that five strains were closely related (99 to 100% identity) to Bacillus subtilis and two were almost identical (99%) to B. megaterium and B. licheniformis. Because the five remaining strains were either closely related (97 to 99% identity) or identical to B. cereus, B. thuringiensis, and B. anthracis, they were classified as belonging to the B. cereus group. Apart from one strain, all clades in the phylogenetic tree were identical to clusters formed in the dendrogram based on biochemical tests results. According to the biochemical profiles, all isolates were characterized as different strains. In addition to chlorine resistance, all isolates were found to be resistant to at least one of five antibiotics tested. These results identify the potential risk of spreading antibiotic resistance genes in the environment by chlorine-resistant strains of Bacillus.

Studies on the secondary metabolites of a Pseudoalteromonas sp. isolated from sediments collected at the northeastern coast of Brazil.

Continuing search for anticancer compounds from the marine environment, we have studied microorganisms that inhabit intertidal sediments of the northeastern Brazilian coast. Of the 32 strains isolated, 13 were selected for biological evaluation of their crude extracts. The acetate extract obtained from a Gram-negative bacterium was strongly active against cancer cell lines with IC(50) values that ranged from 0.04 (HL60 leukemia cells) to 0.26 µg/ml (MDA MB-435 melanoma cells). The bacterium was identified as a Pseudoalteromonas sp. based on 16S rRNA gene sequencing. A bioassay-guided fractionation of the active extract led to the isolation of prodigiosin, a well-known tripyrrole red pigment with immunosuppressive and anticancer activities. Further experiments with ErbB-2 overexpressing cell lines, including HB4a-C3.6 (moderate overexpression), HB4a-C5.2 (high overexpression), and the parental HB4a cell line, were performed. Prodigiosin was moderately active toward HB4a cells with an IC(50) of 4.6 µg/ml, while it was 115 and 18 times more active toward HB4a-C3.6 cells (IC(50) of 0.04 µg/ml) and HB4a-C5.2 (IC(50) of 0.26 µg/ml) cells, respectively. These data suggest that, in spite of its previously described apoptosis-inducing properties, prodigiosin can selectively recognize cells overexpressing ErbB-2, which could be highly appealing in human breast cancer therapy.