ISOLATION AND CHARACTARIZATION OF ANTIBIOTIC PRODUCING BACTERIA FROM SOIL

BELTRAMINO M; CECCHINI NM; CARPINELLA MC; ALBARRACIN ORIO A; LUJÁN AM

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General SAMIGE

Antibiotics have transformed modern medicine. They are essential for treating infectious diseases and enable vital therapies and procedures. However, despite this success, their continued use in the 21st century is risked by the evolution of antibiotic resistance and because the antibiotic development pipeline of major pharmaceutical companies has basically dried up. If the existing situation remains unchanged, then by 2050, 10 million people will die each year from infections previously easily treated with antibiotics. One promising strategy to combat antimicrobial resistance is to search for new antibiotics in nature. Free-living bacteria, particularly those living in the soil or in hostile environments, represent a rich but poorly explored source of antimicrobial compounds. Here, we present a collection of fifty cultured bacteria from soils with different land uses. The soil isolates were screened for antibacterial activity against agricultural (Xhantomonas campestris pv campestris) and human (Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli) pathogens by live co-culture on agar plates or in the presence of sterile supernatants. Amongst all test isolates, five strains obtained from a cotton cultivar showed antibacterial activity against test bacteria. Isolates 4, 10 y 18 showed activity against S. aureus, while isolates 16 and 19 showed antibacterial activity against X. campestris pv campestris and P. aeruginosa, respectively. Maximum antibacterial activity was observed in 48 h supernatants. Phenotypic characterization of antibiotic producing bacteria showed that all were Gram-negative, oxidase-positive and were able to growth in cetrimide but not in bile esculin azide agar. The five strains produced a fluorescent pigment when grown in King B media. Strains 4, 10 and 18 also exhibited the production of a blue pigment similar to P. aeruginosa pyocyanin. However, strains 16 and 19 showed a red and orange-pigmentation, respectively. Although 16S rRNA gene sequencing will be performed for bacterial identification, these results suggest that the five strains obtained are members of the Pseudomonadacea family. Lastly, boiling treatment did not affect antibacterial activity of 4, 10, 16 and 18 supernatants, whereas supernatant from strain 19 lost it activity, i.e. antibacterial activity of the latter could be associated with protein or peptide components. Bioguided fractionation of the above-mentioned supernatants will be carried out in order to isolate and characterize the molecule(s) responsible for the antibacterial activity. These results are encouraging for the search and development of new potential antibiotics to treat life-threatening infections.