3.4.9. Biofilm Formation

A single mutation in a two-component system sensor histidine kinase QseC was generated in biofilm population 2 on day 24 and became fixed. This mutation coincided with a 512–2048-fold increase in MIC from baseline (Table 4). *QseC* is an integral gene of the QseBC two-component system of quorum-sensing with roles in modulating biofilm formation and potentially regulating virulence in KP [43].

## 3.4.10. Mutations with Uncharacterized Function

A mutation in a DUF3413 domain-containing protein was observed following alterations in LPS synthesis genes *lpxC* and *lpxD*, independent of bacterial lifestyle. While the function of this gene is uncharacterized, it was generated by days 15–27 in planktonic and biofilm populations. The mutations in this gene aligned with a 512-fold increase in MIC from baseline for planktonic populations (Table 3). Biofilm population 2 acquired two independent mutations in this gene; one mutation on day 15 corresponded to a 96-fold increase in MIC from baseline, while another mutation that was fixed after day 24 aligned with 512–2048-fold increases in MIC from baseline. A single mutation was observed on day 15 for population 3, with a 128-fold increase in MIC compared to the baseline (Table 4).
