Aims: Forty Bacillus strains isolated from a Brazilian oil reservoir were tested against each other to select strains producing antimicrobial substances (AMS). Three strains, Bacillus subtilis (LFE-1), Bacillus firmus (H 2 O-1) and Bacillus licheniformis (T6-5), were selected due to their ability to inhibit more than 65% of the Bacillus strains tested. These three strains were also investigated for their capability to inhibit sulphate-reducing bacteria (SRB). Furthermore, physiological and biochemical characteristics of the antimicrobial compounds produced by the selected strains were determined. Methods and Results: Among the forty strains tested, 36 (90%) strains were able to inhibit at least one Bacillus strain used as indicator in plate assays and three of them (LFE-1, T6-5 and H 2 O-1) were able to inhibit 65, 70 and 97AE5% of the 40 strains studied here respectively. Clear zones of inhibition were observed when H 2 O-1 was tested against SRB-containing consortium T6-lab and Desulfovibrio alaskensis strain NCIMB 13491, while strain T6-5 was able to inhibit only the D. alaskensis strain. The three substances showed to be insensitive to different enzymes and chemicals, were heat stable and the substances produced by strains T6-5 and H 2 O-1 were active over a wide pH range. Conclusions: Three different AMS produced by Bacillus strains from an oil reservoir, two of them with activity against SRB, are presented here. Significance and Impact of the Study: The preliminary characterization of these AMS points to their potential use as biocides in the petroleum industry for controlling problems associated with SRB.

Sixteen spore forming Gram-positive bacteria were isolated from the rock of an oil reservoir located in a deep-water production basin in Brazil. These strains were identified as belonging to the genus Bacillus using classical biochemical techniques and API 50CH kits, and their identity was confirmed by sequencing of part of the 16S rRNA gene. All strains were tested for oil degradation ability in microplates using Arabian Light and Marlin oils and only seven strains showed positive results in both kinds of oils. They were also able to grow in the presence of carbazole, n-hexadecane and polyalphaolefin (PAO), but not in toluene, as the only carbon sources. The production of key enzymes involved with aromatic hydrocarbons biodegradation process by Bacillus strains (catechol 1,2-dioxygenase and catechol 2,3-dioxygenase) was verified spectrophotometrically by detection of cis,cis-muconic acid and 2-hydroxymuconic semialdehyde, and results indicated that the ortho ring cleavage pathway is preferential. Furthermore, polymerase chain reaction (PCR) products were obtained when the DNA of seven Bacillus strains were screened for the presence of catabolic genes encoding alkane monooxygenase, catechol 1,2-dioxygenase, and/or catechol 2,3-dioxygenase. This is the first study on Bacillus strains isolated from an oil reservoir in Brazil.

The aim of this study was to analyse the effect of oil contamination and biostimulation (soil pH raise, and nitrogen, phosphate and sulphur addition) on the diversity of a bacterial community of an acidic Cambisol under Atlantic Forest. The experiment was based on the enumeration of bacterial populations and hydrocarbon degraders in microcosms through the use of conventional plating techniques and molecular fingerprinting of samples directly from the environment. PCR followed by denaturing gradient gel electrophoresis (DGGE) was used to generate microbial community fingerprints employing 16S rRNA gene as molecular marker. Biostimulation led to increases of soil pH (to 7.0) and of the levels of phosphorus and K, Ca, and Mg. Oil contamination caused an increase in soil organic carbon (170-190% higher than control soil). Total bacterial counts were stable throughout the experiment, while MPN counts of hydrocarbon degraders showed an increase in the biostimulated and oil-contaminated soil samples. Molecular fingerprinting performed with 16S rRNA gene PCR and DGGE analysis revealed stable patterns along the 360 days of experiment, showing little change in oil-contaminated microcosms after 90 days. The DGGE patterns of the biostimulated samples showed severe changes due to decreases in the number of bands as compared to the control samples as from 15 days after addition of nutrients to the soil. Results obtained in the present study indicate that the addition of inorganic compounds to soil in conjunction with oil contamination has a greater impact on the bacterial community than oil contamination only.

The anti-corrosion effect and the antimicrobial activity of lemongrass essential oil (LEO) against the planktonic and sessile growth of a sulfate reducing bacterium (SRB) were evaluated. Minimum inhibitory concentration (MIC) of LEO and its major component, the citral, was 0.17 mg ml-1. In addition, both LEO and citral showed an immediate killing effect against SRB in liquid medium, suggesting that citral is responsible for the antimicrobial activity of LEO against SRB. Transmission electron microscopy revealed that the MIC of LEO caused discernible cell membrane alterations and formed electron-dense inclusions. Neither biofilm formation nor corrosion was observed on carbon steel coupons after LEO treatment. LEO was effective for the control of the planktonic and sessile SRB growth and for the protection of carbon steel coupons against biocorrosion. The application of LEO as a potential biocide for SRB growth control in petroleum reservoirs and, consequently, for souring prevention, and/or as a coating protection against biocorrosion is of great interest for the petroleum industries.

-The potential production of rhamnolipid-type biosurfactants is assessed based on the development of a fermentative process with a strain of Pseudomonas aeruginosa PA1, which was isolated from oil production wastewater in the Northeast of Brazil. These production of molecules using different carbon (n-hexadecane, paraffinic oil, glycerol and babassu oil) and nitrogen sources (NaNO 3 , (NH 4 ) 2 SO 4 and CH 4 N 2 O) was studied. The best results were obtained when using glycerol as substrate. A C/N ratio of 60/1 and use of sodium nitrate as nitrogen source resulted in higher production of the rhamnolipid, expressed by rhamnose (3.16 g/L) and by the yield in relation to biomass (Yp/x = 0.70 g/g). Additionally, physical-chemical characteristics of the spent broth with and without cells were studied, providing a low critical micelle concentration of 19 mg/L and toxicity values of 13 and 13.8 mg/L using two test organisms, the micro crustacean Daphnia similis and the bacterium Vibrio fisheri (Microtox), respectively.