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Protease-producing bacteria isolated from sub-Antarctic marine sediments of Isla de Los Estados (Argentina) were characterized, and the thermal inactivation kinetics of their extracellular proteases compared. Isolates were affiliated with the genera Pseudoalteromonas, Shewanella, Colwellia, Planococcus, and a strain to the family Flavobacteriaceae. Colwellia strains were moderate psychrophiles (optimal growth at about 15 degrees C, maximum growth temperature at around 25 degrees C). 16S rRNA phylogenetic analysis revealed that these strains and Colwellia aestuarii form a distinct lineage within the genus. The remaining isolates were psychrotolerant and grew optimally between 20 and 25 degrees C; two of them represent potentially novel species or genus (16S rRNA < 97% sequence similarity). The thermostability of the extracellular proteases produced by the isolates was analysed, and the inactivation rate constant (k (in)), the activation energy (Ea(in)) and the activation Gibbs free energy of thermal inactivation (Delta G( * ) (in)) determined. Delta G( * ) (in), calculated at 30 degrees C, varied between 97 and 124 kJ/mol. Colwellia enzyme extracts presented the highest thermosensitivity, while the most thermostable protease activity was shown by Shewanella spp. These results demonstrated that the stability to temperature of these enzymes varies considerably among the isolates, suggesting important variations in the thermal properties of the proteases that can coexist in this environment.

A Gram-positive, rod-shaped, spore-forming bacterium (PAT 05 T ) was isolated from the rhizosphere of the perennial shrub Atriplex lampa in north-eastern Patagonia, Argentina. Its overall biochemical and physiological characteristics indicated that this strain should be placed in the alkaliphilic Bacillus group. Strain PAT 05 T grew at pH 7-10 (optimum pH 8), but not at pH 6. Its DNA G+C content was 39?7 mol%. Sequence analysis of the 16S rRNA gene of PAT 05 T revealed the closest match (99?6 % similarity) with Bacillus sp. DSM 8714. The highest level of DNA-DNA relatedness (88?6 %) was also found with this strain. On the basis of 16S rRNA gene sequence similarity and phylogenetic analysis, G+C content and DNA-DNA hybridization data, strain PAT 05 T is related at the species level to Bacillus sp. DSM 8714, a member of a group referred as phenon 4a by Nielsen et al. [Nielsen, P., Fritze, D. & Priest, F. G. (1995). Microbiology 141, 1745-1761], which still lacks taxonomic standing. These results support the proposal of strain PAT 05 T (=DSM 16117 T =ATCC BAA-965 T ) as the type strain of Bacillus patagoniensis sp. nov.

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Shipping operations produce oily wastes that must be managed properly to avoid environmental pollution. The aim of this study was to characterize microorganisms occurring in ship bilge wastes placed in open lagoons and, particularly, to assess their potential to degrade polycyclic aromatic hydrocarbons (PAHs). A first-order kinetic was suitable for describing hydrocarbon biodegradation after 17 days of treatment. The calculated rate constants were 0.0668 and 0.0513 day(-1) with a corresponding half-life of 10.3 and 13.5 days for the aliphatic and aromatic hydrocarbon fractions, respectively. At day 17, PAH removal percentages were: acenaphtylene 100, fluorene 95.2, phenanthrene 93.6, anthracene 70.3, and pyrene 71.5. Methyl phenanthrene removals were lower than that of their parent compound (3-methyl phenanthrene 83.6, 2-methyl phenanthrene 80.8, 1-methyl phenanthrene 77.3, 9-methyl phenanthrene 75.1, and 2,7-dimethyl phenanthrene 76.6). Neither pure cultures nor the microbial community from these wastes showed extracellular biosurfactant production suggesting that the addition of an exogenously produced biosurfactant may be important in enhancing hydrocarbon bioavailability and biodegradation. DNA analysis of bilge waste samples revealed a ubiquitous distribution of the nahAc genotype in the dump pools. Although almost all of the isolates grew on naphthalene as sole carbon source, only some of them yielded nahAc amplification under the experimental conditions used. The variety of PAHs in bilge wastes could support bacteria with multiple degradation pathways and a diversity of catabolic genes divergent from the classical nah-like type.

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