Low and high nucleic acid content bacteria play discrepant roles in response to various carbon supply modes

Abstract

Planktonic bacteria can be grouped into ‘high nucleic acid content (HNA) bacteria’ and ‘low nucleic acid content (LNA) bacteria.’ Nutrient input modes vary in environments, causing nutrient availability heterogeneity. We incubated them with equal amounts of total glucose added in a continuous/pulsed mode. The pulse‐treated LNA bacteria exhibited twice the cell abundance and four times the viability of the continuous‐treated LNA, while HNA did not show an adaptation to pulsed treatment. In structural equation modelling, LNA bacteria had higher path coefficients than HNA, between growth and carbon‐saving metabolic pathways, intracellular ATP and the inorganic energy storage polymer, polyphosphate, indicating their low‐cost growth, and flexible energy storage and utilisation. After incubation, the pulse‐treated LNA bacteria contained more proteins and polysaccharides (0.00064, 0.0012 ng cell−1) than the continuous‐treated LNA (0.00014, 0.00014 ng cell−1), conferring endurance and rapid response to pulses. Compared to LNA, HNA keystone taxa had stronger correlations with the primary glucose metabolism step, glycolysis, and occupied leading positions to explain the random forest model. They are essential to introduce glucose into the element cycling of the whole community under both treatments. Our work outlines a systematic bacterial response to carbon input.