Microbial prospection of communities that produce biosurfactants from the water column and sediments of the Gulf of Mexico.

Microbial communities capable of hydrocarbon degradation linked to biosurfactant (BS) and bioemulsifier (BE) production are basically unexplored in the Gulf of México (GOM). In this work, the BS and BE production of culturable marine bacterial hydrocarbonoclasts consortia isolated from two sites (the Perdido Fold Belt and Coatzacoalcos area) was investigated. The prospection at different locations and depths led to the screening and isolation of a wide variety of bacterial consortia with BS and BE activities, after culture enrichment with crude oil and glycerol as the carbon sources. At least 55 isolated consortia presented reduction in surface tension (ST) and emulsifying activity (EI24 ). After colony purification, bacteria were submitted to polyphasic analysis assays that resulted in the identification of different strains of cultivable Gammaproteobacteria Gram (-) Citrobacter, Enterobacter, Erwinia, Pseudomonas, Vibrio, Shewanella, Thalassospira, Idiomarina, Pseudoalteromonas, Photobacterium, and Gram (+) Staphylococcus, Bacillus, and Microbacterium. Overall, the best results for ST reduction and EI24 were obtained with consortia. Individually, Pseudomonas, Bacillus, and Enterobacter strains showed the best results for the reduction of ST after 6 days, while Thalassospira and Idiomarina strains showed the best results for EI24 (above 68% after 9 days). Consortia isolates from the GOM had the ability to degrade crude oil by up to 40-80% after 24 and 36 months, respectively. In all cases, biodegradation of crude oil was related to the reduction in ST and bioemulsifying activity and was independent from the depth in the water column.

Characterization of Enterobacter cloacae BAGM01 Producing a Thermostable and Alkaline-Tolerant Rhamnolipid Biosurfactant from the Gulf of Mexico.

The search for novel biosurfactants (Bs) requires the isolation of microorganisms from different environments. The Gulf of Mexico (GoM) is a geographical area active in the exploration and exploitation of hydrocarbons. Recent metagenomic and microbiologic studies in this area suggested a potential richness for novel Bs microbial producers. In this work, nineteen bacterial consortia from the GoM were isolated at different depths of the water column and marine sediments. Bs production from four bacterial consortia was detected by the CTAB test and their capacity to reduce surface tension (ST), emulsion index (EI24), and hemolytic activity. These bacterial consortia produced Bs in media supplemented with kerosene, diesel, or sucrose. Cultivable bacteria from these consortia were isolated and identified by bacterial polyphasic characterization. In some consortia, Enterobacter cloacae was the predominant specie. E. cloacae BAGM01 presented Bs activity in minimal medium and was selected to improve its Bs production using a Taguchi and Box-Behnken experimental design; this strain was able to grow and presented Bs activity at 35 g L-1 of NaCl. This Bs decreased ST to around 34.5 ± 0.56 mNm-1 and presented an EI24 of 71 ± 1.27%. Other properties of this Bs were thermal stability, stability in alkaline conditions, and stability at high salinity, conferring important and desirable characteristics in multiple industries. The analysis of the genome of E. cloacae BAGM01 showed the presence of rhlAB genes that have been reported in the synthesis of rhamnolipids, and alkAB genes that are related to the degradation of alkanes. The bioactive molecule was identified as a rhamnolipid after HPLC derivatization, 1H NMR, and UPLC-QTOF-MS analysis.

Phosphatidylcholine synthesis is required for optimal function of Legionella pneumophila virulence determinants.

The function of phosphatidylcholine (PC) in the bacterial cell envelope remains cryptic. We show here that productive interaction of the respiratory pathogen Legionella pneumophila with host cells requires bacterial PC. Synthesis of the lipid in L. pneumophila was shown to occur via either phospholipid N-methyltransferase (PmtA) or phosphatidylcholine synthase (PcsA), but the latter pathway was demonstrated to be of predominant importance. Loss of PC from the cell envelope caused lowered yields of L. pneumophila within macrophages as well as loss of high multiplicity cytotoxicity, while mutants defective in PC synthesis could be complemented either by reintroduction of PcsA or by overproduction of PmtA. The lowered yields and reduced cytotoxicity in mutants with defective PC biosynthesis were due to three related defects. First, there was a poorly functioning Dot/Icm apparatus, which delivers substrates required for intracellular growth into the cytosol of infected cells. Second, there was reduced bacterial binding to macrophages, possibly due to loss of PC or a PC derivative on the bacterium that is recognized by the host cell. Finally, strains lacking PC had low steady-state levels of flagellin protein, a deficit that had been previously associated with the phenotypes of lowered cytotoxicity and poor cellular adhesion.