Relative lack of diversity of microbes recovered on LB Miller agar medium

Abstract Colour of microbial colonies is the first observational clue to microbial identity and type. Although unable to offer much use in microbial classification, diversity of pigmented coloured colonies or lack of on an agar plate still offers useful qualitative understanding of the ability of the medium in recovering diverse microbes from a sample. In general, presence of colonies of monolithic hue (yellow) on an agar plate suggests lack of microbial diversity on the agar plate. This work presents evidence suggesting that LB Miller medium could not usefully recover a diversity of microbes from tap and deionized water. Prior work in the literature has shown a large diversity of microbes able to form differentially coloured colonies on R2A plates from deionized water and tap water samples. Inability of LB Miller agar plates to recover colonies of more than one hue suggests that the medium is unable to recover a large diversity of microbes from environmental water samples. Overall, evidence presented in this work suggests that LB Miller medium is not suitable for use in profiling for microbial diversity in water samples.