Utilization of Semi‐Solid Agar Inoculation in Microbial Co‐Culture: A Novel Protocol for Antibiotic Discovery

Abstract

Microbial co‐culture has many important applications, not least of which being the identification of novel antibiotic factors. However, current co‐culture methods including culture overlay utilizing either the spread or streak plate methods, risk contamination of samples during isolation attempts. Since the bacteria must occupy the same physical space to obtain nutrients, mixed cultures are often obtained during selection of colonies of interest. Semi‐solid agar inoculation co‐culture is an innovative culturing technique which aims to physically separate co‐cultured bacteria to aid in the isolation process. Semi‐solid tryptic soy agar (TSA) with a 1% agar concentration was shown to gellify without difficulty and was able to withstand a variety of culturing methods including lawn culturing, streaking, and point inoculation. Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, and environmental soil microbes inoculated into the semi‐solid agar were able to proliferate and disseminate throughout the entirety of the plate without difficulty. When cultured on top of the inoculated agar, the previously mentioned bacteria grew as expected. Additionally, the resultant colonies exhibited comparable morphology to the same bacteria grown on non‐inoculated agar at typical agar concentration. Due to the ability of secreted factors to diffuse throughout the semi‐solid agar, interactions between the microorganisms, or lack thereof, were readily seen. This technique could prove especially powerful in increasing bacterial yield from environmental samples and aid in antibiotic research and discovery for antibiotic‐resistant priority pathogens (ARPPs).Support or Funding InformationFunded by Divison of Research, Georgia Campus‐Philadelphia College of Osteopathic Medicine.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.