Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed “phototaxis,” enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium
Differential Phototactic Behavior of Closely Related Cyanobacterial Isolates from Yellowstone Hot Spring Biofilms
ABSTRACT Phototrophic biofilms in most environments experience major changes in light levels throughout a diel cycle. Phototaxis can be a useful strategy for optimizing light exposure under these conditions, but little is known about its role in cyanobacteria from thermal springs. We examined two closely related Synechococcus isolates ( Synechococcus OS-A dominates at 60 to 65°C and OS-B′ at 50 to 55°C) from outflows of Octopus Spring in Yellowstone National Park. Both isolates exhibited phototaxis and photokinesis in white light, but with differences in speed and motility bias. OS-B′ exhibited phototaxis toward UVA, blue, green, and red wavelengths, while OS-A primarily exhibited phototaxis toward red and green. OS-A also exhibited negative phototaxis under certain conditions. The repertoires of photoreceptors and signal transduction elements in both isolates were quite different from those characterized in other unicellular cyanobacteria. These differences in the photoresponses between OS-A and OS-B′ in conjunction with in situ observations indicate that phototactic strategies may be quite versatile and finely tuned to the light and local environment. IMPORTANCE Optimizing light absorption is of paramount importance to photosynthetic organisms. Some photosynthetic microbes have evolved a sophisticated process called phototaxis to move toward or away from a light source. In many hot springs in Yellowstone National Park, cyanobacteria thrive in thick, laminated biofilms or microbial mats, where small movements can result in large changes in light exposure. We quantified the light-dependent motility behaviors in isolates representing two of the most abundant and closely related cyanobacterial species from these springs. We found that they exhibited unexpected differences in their speed, directionality, and responses to different intensities or qualities of light. An examination of their genomes revealed several variations from well-studied phototaxis-related genes. Studying these recently isolated cyanobacteria reveals that diverse phototactic strategies can exist even among close relatives in the same environment. It also provides insights into the importance of phototaxis for growth and survival in microbial biofilm communities.
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- NSF-PAR ID:
- 10441797
- Editor(s):
- Alexandre, Gladys
- Date Published:
- Journal Name:
- Applied and Environmental Microbiology
- Volume:
- 88
- Issue:
- 10
- ISSN:
- 0099-2240
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1128/aem.00196-22
