Dibenzothiophene removal by environmental bacteria with differential accumulation of intracellular inorganic polyphosphate.

Dibenzothiophene (DBT), which belongs to the group of polycyclic aromatic heterocycles of sulfur, is a model substance to study the removal of sulfur compounds from oil due to its recalcitrance to traditional and specific removal processes. The aim of this work was to evaluate DBT bioremoval by environmental bacteria and its relationship with polyphosphate (polyP) accumulation, cell surface characteristics and bioemulsifying activity. Pseudomonas sp. P26 achieved the highest DBT removal percentage (48%) after 7 days of incubation. Moreover, positive correlations were estimated between DBT removal and bioemulsifying activity and biofilm formation. A strain-dependent relationship between the content of intracellular polyP and the presence of DBT in the culture medium was also demonstrated. The study of these bacterial characteristics, which could promote DBT transformation, is a first approach to select DBT-removing bacteria, in order to develop bioformulations that are able to contribute to desulfurization processes of petroleum-derived pollutants in the future.

Study of the Extremely-Tolerant Brevibacterium linens AE038-8 with Antiviral Activity Against Herpes Simplex Virus Type 1.

Brevibacterium linens AE038-8 is an arsenic hyper-tolerant bacterial strain, previously isolated from well water in Tucumán, Argentina. The aim of this study was to characterize this strain regarding its resistance to different stress factors and to evaluate its antiviral activity against Herpes simplex virus type 1 (HSV-1). We found that B. linens AE038-8 was capable of tolerating high concentrations of heavy metals such as Cd(II), Cr(VI) and Cu(II). When grown in the presence of NaCl, it could tolerate up to 3 M in LB25 medium. When cultivated, B. linens released to the supernatants a bioactive principle with antiviral activity against HSV-1 virus regardless growth conditions.

Development of low-cost formulations of plant growth-promoting bacteria to be used as inoculants in beneficial agricultural technologies.

Phosphorus is one of the main macronutrients for plant development. Despite its large deposits in soils, it is scarcely available for plants. Phosphate-solubilizing bacteria, belonging to the group of plant growth-promoting rhizobacteria (PGPR), are capable of mobilizing deposits of insoluble phosphates in the soil. The use of PGPR as inoculants provides an environmentally sustainable approach to increase crop production. The effectiveness of inoculants depends on their proper production, formulation and storage in order to ensure the application of the required number of viable microbial cells. In order to develop inexpensive technology, low-cost compounds for biomass production and protection should be used. After the biomass production process, the product should be formulated in a liquid or a solid form, taking into account required storage time, use of protectors/carriers, storage conditions (temperature, humidity, etc.), ease of application and maintenance of beneficial effects on crops. Careful determination of these optimal conditions would ensure a low-cost efficient inoculant that would promote the growth and yield of various crops.

Commensal coagulase-negative Staphylococcus from the udder of healthy cows inhibits biofilm formation of mastitis-related pathogens.

Bovine mastitis, considered the most important cause of economic losses in the dairy industry, is a major concern in veterinary medicine. Staphylococcus aureus and coagulase-negative staphylococci (CNS) are the main pathogens associated with intramammary infections, and bacterial biofilms are suspected to be responsible for the persistence of this disease. CNS from the udder are not necessarily associated with intramammary infections. In fact, some commensal CNS have been shown to have biological activities. This issue led us to screen exoproducts from commensal Staphylococcus chromogenes for anti-biofilm activity against different mastitis pathogens. The cell-free supernatant from S. chromogenes LN1 (LN1-CFS) was confirmed to display a non-biocidal inhibition of pathogenic biofilms. The supernatant was subjected to various treatments to estimate the nature of the biofilm-inhibiting compounds. The results showed that the bioactive compound >5KDa in mass is sensitive to thermal treatment and proteinase K digestion, suggesting its protein properties. LN1-CFS was able to significantly inhibit S. aureus and CNS biofilm formation in a dose-independent manner and without affecting the viability of bovine cells. These findings reveal a new activity of the udder microflora of healthy animals. Studies are underway to purify and identify the anti-biofilm biocompound and to evaluate its biological activity in vivo.

Indigo production by Pseudomonas sp. J26, a marine naphthalene-degrading strain.

A technique developed to determine naphthalene dioxygenase (NDO) activity was optimized and used to study the biotransformation of indole to indigo by Pseudomonas sp. J26 whole cells. The maximum production of indigo was achieved at 25 degrees C using 2.5 mM indole when J26 was grown in the complex medium JPP, while indole concentrations higher than 4 mM proved toxic for cells. The maximum rate of indigo production was 0.56 nmol min(-1) mg dry biomass(-1), obtaining 75.5 microM of indigo after 8 h of incubation, while a maximal concentration (138.1 microM) of indigo was obtained after 20 h.