Bacterial biofilms are complex aggregations of bacteria embedded in a self-produced exopolysaccharide (EPS) matrix. The progression from a planktonic cell to a highly structured biofilm is achieved in five distinct stages with the lifecycle being completed when cells disperse leaving the biofilm to settle elsewhere. P. inhibins is an effective colonizer of marine surfaces and has the ability to outcompete other microbiota due, in part, to the secondary metabolite tropodithietic acid (TDA). Like other bacteria, P. inhibins produces heritable phenotypic variants during the dispersal phase of biofilm growth. Among the resulting dispersal variants are white variants that exhibit reduced competition against the co-occurring bacterium Pseudoalteromonas tunicata. This study aimed to investigate the interactions of P. inhibins wild-type (WT), P. inhibins white variant and P. tunicata when grown as single-species and in co-culture biofilms and to determine the genetic basis behind the P. inhibins white variant. P. inhibins WT and white variant biofilms were grown in a continuous flow cell system for 12 days. Fluorescently tagged strains were used to visualize the biofilms. Confocal laser scanning microscopy analysis indicated that both P. inhibins WT and P. inhibins white variant grew in equal proportions. The genome of the P. inhibins white variant was sequenced to assess the genetic differences between it and the original P. inhibins WT strain. Sequencing reads where aligned to the reference genome using Novocraft and single nucleotide polymorphisms (SNPs) were called using the R-package deepSNV. Sequencing of the white variant revealed point mutations in genes affecting GDP-mannose 4,6-dehydratase (GMD), DNA replication and repair protein (recF) and cell division protein (ftsA). Studies of functional diversification in microbial biofilms and the mechanisms by which it occurs will contribute to a better understanding of microbial evolutionary processes, the adaptability of microbial populations, and how to design biofilm control systems.