THE FIGHT AGAINST PATHOGENS IS NOT OVER: ARGENTINE ANTARCTIC EXPEDITIONS DISCLOSE A NOVEL SOURCE FOR COLD - ACTIVE ANTIMICROBIAL BIOPROSPECTING

DANILOVICH, M.E; ACOSTA, F.; SANCHEZ L. A,; DELGADO O.D.

Mar del Plata

Congreso; X CONGRESO ARGENTINO DE MICROBIOLOGIA GENERAL SAMIGE; 2014

Sociedad Argentina de Microbiología General SAMIGE

An organism that lives in an extreme environment is an extremophile. Within extremophiles we can find organisms belonging to archaea, prokaryotes and eukaryotes. Key factors, such as frequent and inappropriate use of antibiotic causing increase in bacterial resistance to those commonly used, as well as an irregular emergence generated from a detriment of pharmaceutical companies involved in drugs discovery, makes the development of new antibiotics is a growing worldwide problem and a constant challenge. The need to reduce additives in food industry has triggered the pursuit of natural antimicrobial substances produced by microorganisms from different sources with the aim of preserving processed foods by inhibiting microorganisms associated with food-borne illness. Most antibiotics emerged from screening programs of natural sources, including the isolation of new microorganisms, modification of well-known producers or metabolic engineering of fermentation processes. Extremophiles are considered an important source of metabolites, enzymes and bio-products since they are adapted to their unusual living conditions. This work focused on the isolation of psychrotolerant and psychrophilic microorganisms producing cold-active substances with the ability to inhibit the growth of common food-borne pathogens and phytopatogens for potential use in food preservation, pharmaceutical industry or as agriceutical. Twenty-seven antimicrobial producers were isolated by using microbiological selection techniques from sea water and sediment samples obtained during the 2011 and 2014 summer Antarctic campaigns of the oceanographic survey ship ARA Puerto Deseado. Isolates were grouped in 11 OTUs by ITS-ARDRA techniques; four of them were selected for identification based on rDNA regions sequence analysis together with the biochemical characterization. Isolates 2D, 5D and 6D were closely related to Halomonas titanicae (99.8, 98.9, 96.7% respectively), whilst isolate 18SH was related to Candida sake (99%). Antimicrobials produced by isolates 2D, 5D and 6D exhibited low molecular weight (<6,000 Da) and inhibition spectrum against both, Gram (+) and Gram (-) pathogenic bacteria. The antagonist compound produced by Candida sake 18SH showed a higher molecular weight (˃12,000 Da) and a narrower spectrum of bacterial inhibition. However, antagonistic activity against fungi causing rots in fruits was detected. Due to its potential as plant pathogen biocontrol agent was selected for further characterization. Studies indicate antimicrobial stability in 5.0-7.0 pH range and 4-45°C temperature range. Antimicrobial activity was detected during early stationary growth phase retaining antimicrobial activity at low temperatures. To purify the antimicrobial, a protocol involving solid-phase C18 cartridges and HPLC was developed. This work highlights cold environments as a suitable source of microorganisms with the ability to produce cold-active biomolecules of biotechnological interest.