Biology subjects

Suban, S.

Publications and source records attributed to Suban, S..

3 recordsLinked to original sources

bioRxiv2023

Cyanobacterial sigma factor controls biofilm-promoting genes through intra- and intercellular pathways

Cyanobacteria frequently constitute integral components of microbial communities known as phototrophic biofilms. These assemblages are not only widespread in various environmental contexts but also hold significant industrial relevance. Nevertheless, the governing elements responsible for cyanobacterial biofilm development have remained elusive. This study, which employs the model cyanobacterium Synechococcus elongatus PCC 7942, demonstrates that the RNA polymerase sigma factor SigF1, but not its paralog SigF2, is required for a biofilm-suppression mechanism that operates in this organism. Comprehensive transcriptome analyses identified distinct regulons under the control of each of these sigma factors. Additional data indicate that SigF1 regulates biofilm through its involvement in transcriptional induction of genes that include those for the primary pilus subunit: sigF1 inactivation both prevents pilus assembly and abrogates secretion of a biofilm inhibitor. Consequently, expression is significantly upregulated for the ebfG-operon that encodes matrix components and the genes that encode their corresponding secretion system. Thus, this study uncovers a basic regulatory component of cyanobacterial communal behavior. Elevated expression of biofilm-promoting genes in a sigF1 mutant supports an additional layer of regulation by SigF1 that operates via an intracellular mechanism.

microbiology↗

bioRxiv2022

Transcriptomic and phenomic investigations reveal elements in biofilm repression and formation in the cyanobacterium Synechococcus elongatus PCC 7942

Biofilm formation by photosynthetic organisms is a complex behavior that serves multiple functions in the environment. Biofilm formation in the unicellular cyanobacterium Synechococcus elongatus PCC 7942 is regulated in part by a set of small secreted proteins that promotes biofilm formation and a self-suppression mechanism that prevents their expression. Little is known about the regulatory and structural components of the biofilms in PCC 7942, or response to the suppressor signal(s). We performed transcriptomics (RNA-Seq) and phenomics (RB-TnSeq) screens that identified four genes involved in biofilm formation and regulation, more than 25 additional candidates that may impact biofilm formation, and revealed the transcriptomic adaptation to the biofilm state. In so doing, we compared the effectiveness of these two approaches for gene discovery.

microbiology↗

bioRxiv2021

Impairment of a cyanobacterial glycosyltransferase that modifies a pilin results in biofilm development

A biofilm inhibiting mechanism operates in the cyanobacterium Synechococcus elongatus. Here, we demonstrate that the glycosyltransferase homolog, Ogt, participates in the inhibitory process - inactivation of ogt results in robust biofilm formation. Furthermore, a mutational approach shows requirement of the glycosyltransferase activity for biofilm inhibition. This enzyme is necessary for glycosylation of the pilus subunit and for adequate pilus formation. In contrast to wild-type culture in which most cells exhibit several pili, only 25% of the mutant cells are piliated, half of which possess a single pilus. In spite of this poor piliation, natural DNA competence was similar to that of wild-type, therefore, we propose that the unglycosylated pili facilitate DNA transformation. Additionally, conditioned medium from wild-type culture, which contains a biofilm inhibiting substance(s), only partially blocks biofilm development by the ogt-mutant. Thus, we suggest that inactivation of ogt affects multiple processes including production or secretion of the inhibitor as well as the ability to sense or respond to it. Originality-Significance StatementThe molecular mechanisms that underlie biofilm development in cyanobacteria are just emerging. Using the cyanobacterium S. elongatus as a model, we demonstrate that glycosylation of the pilus subunit is crucial for the biofilm self-suppression mechanism, however, it is dispensable for DNA competence.

microbiology↗