Pseudomonas sp. 8H1 producing a cold-active antimicrobial compound. Characterization and production in different culture media.

ARNAU VG; SANCHEZ LA; DELGADO OD

Mar del Plata

Congreso; VIII Congreso de Microbiologia General; 2012

Sociedad Argentina de Microbiologia General

Antimicrobials are molecules widespread in life forms to mediate competition, and their industrial production could be important for the potential use as preservatives in food, cosmetic and pharmaceutical industries. Cold environments could be a suitable source of microorganisms with the ability to produce cold-active antimicrobials with a potential use as chilled-food preservation. Isolate 8H1 was collected from Isla de los Estados (South Atlantic Argentina; 54°S, 63°47' - 65°46'W). Its ability to produce cold active antimicrobials and inhibition spectrum against pathogenic strains were determined by the deferred antagonism procedure. Low temperature activity was evaluated by using S. proteamaculans 136 as sensitive strain. Bacterial characterization included Gram staining, morphology, growth temperature, NaCl and pH tolerance; sugar fermentation, catalase, oxidase and some other features were carried out by using API systems (bioMérieux, France). 16S rDNA and gyrB sequence and G+C content were also determined. Optimum antimicrobial production (expressed as arbitrary units per milliliter and/or specific activity) was evaluated in different culture media: LB, LB+glucose and R2A. Antimicrobial nature; thermo-stability and pH-stability/activity were tested. Antimicrobial size was estimated after diffusion through different cut-off dialysis membrane. Isolate 8H1 is a Gram- negative, rod-shaped, psychrotolerant bacterium; according to 16S rDNA and gyrB sequences it is close related to Pseudomonas fluorescens group (97.95% and 94.45% identities, respectively) with a G+C content of 59.8 mol%. The inhibitor was effective against both Gram+ and Gram-: E. coli, Pseudomonas aeruginosa, Salmonella enterica ser. Newport, S. enterica ser. Typhimurium, Listeria monocytogenes, Shigella sonnei, S. flexneri, Staphylococcus aureus, S. epidermidis, Enterobacter aerogenes, E. cloacae, Citrobacter freundii and Proteus mirabilis. Furthermore, isolate 8H1 was able to inhibit the growth of S. proteamaculans 136 at low temperature. The production of antimicrobial was higher in R2A medium at 8°C (100 AU mL-1 and 167x103 AU g dry cell-1) than in the other studied culture media. Antimicrobial compound was not sensitive to the assayed enzymes, indicating that activity was not due to hydrogen peroxide, lipid or glycan moieties or acid. It was also not affected by the proteases tested, a fact probably due to the small molecular size (<2,000 Da). In addition, it has wide pH-stability (pH 3-9) and thermo-stability (-20-55°C).