Elongation Correlates with Nutrient Deprivation in Pseudomonas aeruginosa-Unsaturated Biofilms

• Published in: Microbial ecology Vol. 43; no. 4; pp. 416 - 423
• Main Authors: R. E. Steinberger, Allen, A. R., Hansma, H. G., P. A. Holden
• Format: Journal Article
• Language: English
• Published: New York, NY Springer-Verlag New York Inc 01.06.2002; Springer
• Subjects: Action of physical and chemical agents on bacteria; Animal, plant and microbial ecology; Bacteria; Bacteriology; Bioavailability; Biofilms; Biological and medical sciences; Cell growth; Fundamental and applied biological sciences. Psychology; Liquids; Microbial ecology; Microbiology; Nutrients; P branes; Ratios; Starvation; Surface areas; Various environments (extraatmospheric space, air, water); Pseudomonadales; Availability; Terrestrial environment; Atomic force microscopy; Nutrition; Plant leaf; Plant; Morphology; Biofilm; Bacteria; Pseudomonadaceae; Environment; Nutrient; Pseudomonas aeruginosa; Elongation
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-001-1063-z

Bacteria in nature frequently grow as biofilms, yet little is known regarding how biofilm bacteria morphologically adapt to low nutrient availability, which is common in unsaturated environments such as the terrestrial subsurface or on plant leaves. For unsaturated biofilms, in which the substratum may provide all nutrients, what are the relationships between nutrition and cell size and shape-the simplest metrics of cellular morphology? To address this question, we cultured Pseudomonas aeruginosa, a ubiquitous gram-negative bacterium that is environmentally and medically important, on membranes overlaying solid media, and then measured cellular dimensions using atomic force microscopy (AFM). Nutrition was controlled chemically by media composition and physically by stacking membranes to increase the path length for nutrient diffusion. Under conditions of carbon-nitrogen imbalance, low carbon bioavailability, or increased nutrient diffusional path length, cells elongated while maintaining constant width. A mathematical relationship suggests that, by elongating, biofilm bacteria strategically enlarge their nutrient collection surface without substantially changing the ratio of surface area to volume (SA/V). We conclude that P. aeruginosa growing as unsaturated biofilm with a planar nutrient source morphologically adapt to starvation by elongating. This adaptation, if generalizable, differs from a better-understood starvation response (i.e., cell size decreases; thus SA/V increases) for planktonic bacteria in well-mixed environments.