Modification of nutrient agar medium to culture yet-unculturable bacteria living in unsanitary landfills

Abstract

The microbial diversity in waste dumps is considered to be high. Generally, ca. 99% of bacterial species remain unculturable in standard media. This research was focused to modify Nutrient Agar (NA) mimicking the natural substrate where bacteria actually live. NA medium was modified by adding 40% (M1), 32% (M2), 24% (M3), 16% (M4), and 8% (M5) (v/v) soil extracts obtained from the dump site to isolate its bacteria. Conventional NA was the control. The isolates were characterized by FTIR spectroscopy. Seventy-eight and 18 bacterial strains were isolated from the modified media (M1-M5) and the control, respectively. Absorbance of the FTIR spectra constituted six clusters. According to the cluster analysis, the 100% similarity was observed in three bacterial couples, which were considered as three strains. Thus, the modified media of the present study facilitated the culturing of 75 unculturable bacterial strains over the conventional NA and percent improvement of isolation was 417% over NA. Results revealed the potential of extracted soil biochemicals and nutrients to modify the NA for culturing yet-unculturable bacteria living in unsanitary landfills.

Keywords

• unculturable bacteria, soil extracts, nutrient agar, ftir