Genomic and phenotypic features of Acinetobacter baumannii isolated from oil reservoirs reveal a novel subspecies specialized in degrading hazardous hydrocarbons.

The genus Acinetobacter encompasses biotechnologically relevant species and nosocomial pathogens. In this study, nine isolates recovered from different oil reservoir samples showed the ability to grow with petroleum as the only carbon source and possessed the ability to emulsify kerosene. The whole genomes of the nine strains were sequenced and analyzed. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of all strains were compared to the reference strains, and the results were below the reference values (<97.88 and 82, respectively), suggesting that the isolates belong to a new subspecies of Acinetobacter baumannii. The name Acinetobacter baumannii oleum ficedula is proposed. A comparison of the whole genome repertoire of 290 Acinetobacter species indicated that the strains in this study resemble non-pathogenic Acinetobacter strains. However, the new isolates resemble A. baumannii when comparing virulence factors. The isolates in this study carry many genes involved in hydrocarbon degradation, indicating the potential to degrade most toxic compounds listed by environmental regulatory agencies such as ATSDR, EPA, and CONAMA. In addition, despite the absence of known biosurfactant or bioemulsifier genes, the strains showed emulsifying activity, suggesting the presence of new pathways or genes related to this process. This study investigated the genomic, phenotypic, and biochemical features of the novel environmental subspecies A. baumannii oleum ficedula, revealing their potential to degrade hydrocarbons and to produce biosurfactants or bioemulsifiers. Applying these environmental subspecies in bioaugmentation strategies sheds light on future approaches to bioremediation. The study shows the importance of genomic analysis of environmental strains and their inclusion in metabolic pathways databases, highlighting unique enzymes/alternative pathways for consuming hazardous hydrocarbons.

Microbial Culture in Minimal Medium With Oil Favors Enrichment of Biosurfactant Producing Genes.

The waste produced by petrochemical industries has a significant environmental impact. Biotechnological approaches offer promising alternatives for waste treatment in a sustainable and environment-friendly manner. Microbial consortia potentially clean up the wastes through degradation of hydrocarbons using biosurfactants as adjuvants. In this work, microbial consortia were obtained from a production water (PW) sample from a Brazilian oil reservoir using enrichment and selection approaches in the presence of oil as carbon source. A consortium was obtained using Bushnell-Haas (BH) mineral medium with petroleum. In parallel, another consortium was obtained in yeast extract peptone dextrose (YPD)-rich medium and was subsequently compared to the BH mineral medium with petroleum. Metagenomic sequencing of these microbial communities showed that the BH consortium was less diverse and predominantly composed of Brevibacillus genus members, while the YPD consortium was taxonomically more diverse. Functional annotation revealed that the BH consortium was enriched with genes involved in biosurfactant synthesis, while the YPD consortium presented higher abundance of hydrocarbon degradation genes. The comparison of these two consortia against consortia available in public databases confirmed the enrichment of biosurfactant genes in the BH consortium. Functional assays showed that the BH consortium exhibits high cellular hydrophobicity and formation of stable emulsions, suggesting that oil uptake by microorganisms might be favored by biosurfactants. In contrast, the YPD consortium was more efficient than the BH consortium in reducing interfacial tension. Despite the genetic differences between the consortia, analysis by a gas chromatography-flame ionization detector showed few significant differences regarding the hydrocarbon degradation rates. Specifically, the YPD consortium presented higher degradation rates of C12 to C14 alkanes, while the BH consortium showed a significant increase in the degradation of some polycyclic aromatic hydrocarbons (PAHs). These data suggest that the enrichment of biosurfactant genes in the BH consortium could promote efficient hydrocarbon degradation, despite its lower taxonomical diversity compared to the consortium enriched in YPD medium. Together, these results showed that cultivation in a minimal medium supplemented with oil was an efficient strategy in selecting biosurfactant-producing microorganisms and highlighted the biotechnological potential of these bacterial consortia in waste treatment and bioremediation of impacted areas.

Characterization and aqueous extraction of calcium hydroxide materials.

Analysis of two single and eight dual product systems showed the former to be calcium hydroxide dispersed in an aqueous gel in methyl ethyl ketone solution of an acrylic polymer and the latter were cements based on the polymerization occurring when mixing salicylate esters with calcium hydroxide. Using water as an extractant under controlled conditions, specimens of the prepared materials produced marked differences in pH values over 24 hours and conductivity over 72 hours; also cumulative extractions over 26 weeks showed substantial variation in the amount of calcium hydroxide and other solubles.

Potential toxicants in alginate powders.

Twenty-five dental alginate impression powders were obtained locally and analysed for Pb, Zn, Ba, Cd, As, Be, Hg, Sb, and V contents by atomic absorption spectroscopy; also total fluoride was determined by a conventional wet-way procedure. In addition, some lead containing powders were investigated for the lead content of the aerosol and that extractable from the surface of the set material by aqueous solutions. The results are detailed and concern is expressed at a possible hazard to health, mainly by inhalation of these materials.

A survey of the elemental composition of alloy for dental amalgam.

Analyses of 51 alloys (conventional, 41, and high-copper, 10) currently available in Australia were made. A rapid and precise procedure was developed that relied on wet-way methods for silver and tin while copper, zinc, mercury, indium and low-level constituents, such as lead, cadmium and antimony, were determined by atomic absorption spectroscopy. The conventional alloys, with two minor exceptions, all complied with the compositional requirements of modern standards and little quantitative variations was noted when the range of the major component was compared with the values obtained in two surveys made over thirty years ago. The high-copper contained, among other factors, an average copper concentration about four times that of conventional alloys. Rather surprising were the contents of mercury, indium, and cadmium found in some of the alloys as well as the low-level concentration of lead, and in a few cases antimony. Other elements were not detected by the sensitive technique used. It is justifiable to recommend that the maximum zinc content to be permitted in zinc-free type alloys should not be greater than 0.01%, and this value was subsequently incorporated in the revised Australian standard 2110-1977: Alloy for Dental Amalgam.

A rapid spectrophotometric assay of amide type dental anaesthetic agents.

A spectrophotometric procedure for the determination of lignocaine in ointments was investigated and standardized for general application to local anaesthetic solutions of the amide type commonly used for dental injection, namely, lignocaine, prilocaine, mepivacaine, pyrrocaine and tolycaine. The method is based on the controlled formation of a copper complex and the Beer-Lambert law was found to be obeyed over a useful range. Results indicated that the method would be accurate, convenient and rapid, saving substantial time over wet-way methods conventionally used. For confirmation of the identify of the anaesthetic agent, infrared spectroscopy was shown to be a rewarding technique.