Spatio-temporal formation of biofilms and extracellular matrix analysis in Azospirillum brasilense

• Published in: FEMS microbiology letters Vol. 367; no. 4; pp. 1 - 10
• Main Authors: Viruega-Góngora, Víctor I, Acatitla-Jácome, Iris S, Reyes-Carmona, Sandra R, Baca, Beatriz E, Ramírez-Mata, Alberto
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.02.2020
• Subjects: Agronomy; Azospirillum brasilense; Azospirillum brasilense - growth & development; Azospirillum brasilense - physiology; Bacterial Outer Membrane Proteins - metabolism; Biofilms; Biofilms - growth & development; Cell culture; Colonization; Confocal microscopy; Deoxyribonucleic acid; DNA; DNA, Bacterial - metabolism; Exopolysaccharides; Extracellular matrix; Extracellular Polymeric Substance Matrix - metabolism; Flagella; Flagellin; Flagellin - metabolism; Fluorescence; Fluorescence microscopy; Gene regulation; Immunofluorescence; Kinetics; Matrix methods; Membrane proteins; Microbial mats; Microbiology; Microscopy; Microscopy, Confocal; Microscopy, Fluorescence; Morphology; Physiological aspects; Plant growth; Polysaccharides, Bacterial - metabolism; Proteobacteria; Scanning microscopy; Mexico; exopolysaccharides; biofilm formation; OmaA; eDNA; polar flagellum; extracellular matrix; Azospirillum
• ISSN: 1574-6968; 0378-1097; 1574-6968
• DOI: 10.1093/femsle/fnaa037

ABSTRACT Elucidation of biofilm structure formation in the plant growth-promoting rhizobacterium Azospirillum brasilense is necessary to gain a better understanding of the growth of cells within the extracellular matrix and its role in the colonization of plants of agronomic importance. We used immunofluorescence microscopy and confocal laser scanning microscopy to study spatio-temporal biofilm formation on an abiotic surface. Observations facilitated by fluorescence microscopy revealed the presence of polar flagellin, exopolysaccharides, outer major membrane protein (OmaA) and extracellular DNA in the Azospirillum biofilm matrix. In static culture conditions, the polar flagellum disaggregated after 3 days of biofilm growth, but exopolysaccharides were increasing. These findings suggest that the first step in biofilm formation may be attachment, in which the bacterium first makes contact with a surface through its polar flagellum. After attaching to the surface, the long flagella and OmaA intertwine the cells to form a network. These bacterial aggregates initiate biofilm development. The underlying mechanisms dictating how the biofilm matrix components of A. brasilense direct the overall morphology of the biofilm are not well known. The methods developed here might be useful in further studies that analyze the differential spatial regulation of genes encoding matrix components that drive biofilm construction. Kinetics of Azospirillum brasilense Sp7 biofilm formation on an abiotic surface, showing cells (DAPI - blue) and flagella (FITC-labeled antibody - green) in the fluorescence microscope.