Validating metagenomic growth rate indicators in a coastal marine microbial community

Growth rates are fundamental properties of all organisms and necessary for ecological characterization of microorganisms, but for most natural microorganisms we do not know their growth rates in nature nor even their maximum growth rate. 'Omics-based techniques can be leveraged to estimate DNA replication rates and maximum growth rates. We performed experiments in order to test and/or validate these approaches. We started by preparing grazer-free, virus-free seawater diluted surface samples from the San Pedro Channel, CA, and incubated them with the objective of observing microbial growth. At multiple time points, we sampled for total cell counts and DNA, which was sequenced. Metagenome-assembled genomes (MAGs) were generated by a variety of techniques, resulting in numerous unique MAGs. The percentage of total metagenomic reads mapping to each MAG was normalized with total cell counts to estimate the growth rate of each MAG or individual taxa.