Klebsiella pneumoniae capsule promotes survival in starvation conditions
Klebsiella pneumoniae is a priority opportunistic pathogen that is found in soil, water and plant-associated niches as well as associated with humans. Host fitness factors of K. pneumoniae include a highly diverse polysaccharide capsule, siderophores and fimbriae, among others, however little is known about how this pathogen survives outside the host. We conducted genome-scale fitness screening to explore survival mechanisms of K. pneumoniae ATCC43816 in fresh water. Unexpectedly, the Type K2 capsule of this strain was revealed to be the primary determinant of proliferation or survival in this environment. Capsulated cells had a survival advantage in carbon-starved conditions that was accompanied by a reduction in capsule size over time, and was negated by carbon supplementation. Transcriptomics and reporter assays were consistent with catabolism of capsule constituents.