Archaeal Tubulin-like Proteins Modify Cell Shape in during Early Biofilm Development.

Tubulin, an extensively studied self-assembling protein, forms filaments in eukaryotic cells that affect cell shape, among other functions. The model archaeon uses two tubulin-like proteins (FtsZ1/FtsZ2) for cell division, similar to bacteria, but has an additional six related tubulins called CetZ. One of them, CetZ1, was shown to play a role in cell shape. Typically, discoid and rod shapes are observed in planktonic growth, but under biofilm formation conditions (i.e., attached to a substratum), can grow filamentously. Here, we show that the deletion mutants of all eight tubulin-like genes significantly impacted morphology when cells were allowed to form a biofilm. , , and created longer, less round cells than the parental and a higher percentage of filaments. and were significantly rounder than the parental, and generated larger, flat, amorphic cells. The results show all tubulin homologs affect morphology at most timepoints, which therefore suggests these genes indeed have a function.