Is there an infant mortality in bacteria?

TL;DR

This paper investigates whether infant mortality occurs in bacteria, providing evidence of significant mortality rates around cell division and proposing experiments to measure age-specific death rates in E. coli.

Contribution

It offers the first consistent evidence of infant mortality in bacteria and outlines a novel experimental approach to measure age-specific death rates post-division.

Findings

Evidence of a mortality rate of about 0.7 per 1,000 per hour in E. coli

Recent experiments suggest infant mortality occurs in bacteria during exponential growth

Proposed flow cytometry method to measure age-specific death rates in bacteria

Abstract

This manuscript proposes a significant step in our long-run investigation of infant mortality across species. Since 2016 (Berrut et al. 2016) a succession of studies (Bois et al. 2019) have traced infant mortality from organisms of high complexity (e.g. mammals) down to unicellular organisms. Infant mortality may be considered as a filtering process through which organisms with potentially lethal congenital defects are eliminated. Such defects may have many causes but here we focus particularly on mishaps resulting from non-optimal conditions in the production of proteins, enzymes and other crucial macromolecules. The statistical signature of infant mortality consists in a falling age-specific death rate. The question we address here is whether infant mortality episodes take place in bacteria in the minutes precededing or following cell division. It will be shown that while experiments carried out in the 20th century tried but failed to detect such an effect (mostly because of limited sample size), more recent observations provided consistent evidence of a sizeable mortality, with a rate of the order of 0.7 per 1,000 per hour, in the exponential growth phase of E. coli. A further crucial test will be to measure the age-specific, post-division death rate. An experiment is outlined for that purpose. It is based on the selection of stained cells through flow cytometry and the derivation of their ages at death from their sizes. If an infant mortality effect can be identified in E. coli it can be conjectured that a similar effect also exists in other unicellular organisms, both prokaryote and eukaryote.