engleski

Size of Escherichia coli dependent on the media used for cultivation

E. coli DSM 498 was precultivated on the Tryptic glucose yeast agar (Biolife, Italy) at 36±0.1°C/2d. Biomass was subcultured and incubated at 36±0.1°C/2d on/in 8 different commercial media suitable for the cultivation of E. coli (Biolife, Italy): Nutrient agar, EC X-GLUC agar, Endo agar, Mac Conkey agar, Mac Conkey broth, m-Faecal Coliform agar, m-LES Endo agar, TTC Tergitol 7 agar base. The culture of E. coli from each medium was stained by Gram method and examined by light microscopy with magnification of 7520x. The length and width of bacteria were determined using DinoCapture 2.0 software by measuring at least 100 cells per medium. The cells of E. coli cultivated on the media with proteins as the carbon source (Nutrient agar and EC X-GLUC agar) had an average length of 1.592±0.338 m, width 0.651±0.106 m and width/length ratio 0.422±0.086. The cells of E. coli cultivated on/in the media with proteins and lactose as the carbon sources (Endo agar, Mac Conkey agar, Mac Conkey broth, m-Faecal Coliform agar, m-LES Endo agar, TTC Tergitol 7 agar base) were statistically significant longer with an average length of 3.595±1.193 m, wider with 0.680±0.131 m and with lower width/length ratio of 0.202±0.050. In the literature the cells belonging to the genus Ecsherichia are generally described as straight cylindrical rods 2.0-6.0 x 1.1-1.5 m. The size of E. coli varies when cultivated on/in different commercial media. Although the size of E. coli is not a determinative characteristic, the variation of cell size when cultured on/in different commercial media can be of great help during routine laboratory work.

Escherichia coli; cultivation; microscopy; width; length

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