Cellular stress can induce substantial physiological and molecular adaptations to ensure survival. Depending on the stress dose and length of exposure, the flagella of the unicellular chlorophyte Chlamydomonas reinhardtii are paralyzed or lost (Hessen et al., 1995; Dharmadhikari et al., 2006), and later cells manifest ‘palmelloids’ (Jamers & De Coen, 2010 and references therein) or apoptose (Moharikar et al., 2006, 2007; Yordanova et al., 2010). Palmelloids are a stress-responsive temporary, dormant ‘colonial’ stage with characteristic physiological changes such as exopolysaccharide secretion, clustering of cells embedded in an exopolysaccharide mesh and a common membrane, individual cell wall thickening, abnormal cell division, change in cell morphology and decrease in cell viability (Nakamura et al., 1976; Lewin, 1984; Visviki & Santikul, 2000; Jamers & De Coen, 2010). Microarray analysis of paraquat-treated C. reinhardtii palmelloids showed differential regulation of genes (Jamers & De Coen, 2010) indicating alterations in both cell phenotype and transcriptome, facilitating cells to devise strategies for survival or death. Although the molecular mechanisms that regulate palmelloid formation in Chlamydomonas species remain elusive, some of the physiological hallmarks are conserved. Like most other eukaryotes, C. reinhardtii harbors conserved stress-responsive gene families, making it a suitable system to study the molecular mechanisms that underlie palmelloid formation. Akin to palmelloidy, biofilms are defined as a structured community of bacterial cells enclosed in a self-produced polymeric matrix that adhere to a living or inert surface (Watnick & Kolter, 2000) and exhibit altered phenotype, changing growth rate and gene transcription. Parallels between biofilms and palmelloids are: (1) secretion of high levels of exopolysaccharides (Kobayashi, 2007; Shemesh et al., 2010; Yoon et al., 2011); (2) alterations in cell morphology (Kobayashi, 2007; Yoon et al., 2011); (3) effects on cell wall biogenesis (Shemesh et al., 2010; Daher et al., 2011); (4) relations with flagella (Prigent-Combaret et al., 2000; Klausen et al., 2003; Lemon et al., 2007); and (5) stress induction (Rode et al., 2007; Kaplan, 2011). Microarray analysis to study biofilm formation in Escherichia coli has reported ∼ 150 differentially expressed genes (Niba et al., 2007). Furthermore, biofilm formation in E. coli at 23 °C was regulated by adrA, nhaR, mlrA, csgA and bolA genes (White-Ziegler et al., 2008). A search for homologs in C. reinhardtii resulted in five putative bolA-like genes. In E. coli, the BolA protein was first studied as a morphogene that could promote round morphology in cells when over-expressed (Aldea et al., 1988). The gene was found to be regulated by growth phase-dependent promoter P1, induced during the transition to stationary phase of growth. It was found to be under the control of RpoS (Hengge-Aronis et al., 1993). Exposure to several stresses up-regulated bolA gene even in the early logarithmic phase (Santos et al., 1999), suggesting an important role in stress response. As a transcriptional regulator, it was found to independently regulate the transcription of dacA and dacC carboxypeptidases, a β-lactamase ampC (Santos et al., 2002; Guinote et al., 2011) and the actin-like gene mreB (Freire et al., 2009); genes involved in different activities of cell morphology and division. The 3-D structures of BolA protein from Mus musculus and Xanthomonas campestris pv. campestris confirmed the presence of the DNA-binding Class II KH fold, supporting a regulatory role (Kasai et al., 2004; Chin et al., 2005). BolA protein over-expression in E. coli facilitated biofilm formation in a stress-responsive manner (Vieira et al., 2004). In Shizosaccharomyces pombe, uvi31+, a bolA homolog was up-regulated under UV light and an involvement in the regulation of cell septation and cytokinesis was suggested (Kim et al., 1997, 2002). Although in silico searches of three human homologs (HsBolA) showed no signal peptide for secretion, experimental analysis showed secretion of the proteins from Cos-7 cells (Zhou et al., 2008). The widespread occurrence and conservation of the bolA gene family across different genera prompted us to explore the function of an as yet elusive algal bolA-like gene. The current study attempts to functionally dissect the role of a C. reinhardtii BolA-like protein by cloning the gene (CrbolA), over-express the protein (CrBolA) in E. coli, and study the possible effect on morphology and biofilm formation.