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Evanescent photosynthesis: exciting cyanobacteria in a surface-confined light field.
MedLine Citation:
PMID:  22395147     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The conversion of solar energy to chemical energy useful for maintaining cellular function in photosynthetic algae and cyanobacteria relies critically on light delivery to the microorganisms. Conventional direct irradiation of a bulk suspension leads to non-uniform light distribution within a strongly absorbing culture, and related inefficiencies. The study of small colonies of cells in controlled microenvironments would benefit from control over wavelength, intensity, and location of light energy on the scale of the microorganism. Here we demonstrate that the evanescent light field, confined near the surface of a waveguide, can be used to direct light into cyanobacteria and successfully drive photosynthesis. The method is enabled by the synergy between the penetration depth of the evanescent field and the size of the photosynthetic bacterium, both on the order of micrometres. Wild type Synechococcus elongatus (ATCC 33912) cells are exposed to evanescent light generated through total internal reflection of red (λ = 633 nm) light on a prism surface. Growth onset is consistently observed at intensity levels of 79 ± 10 W m(-2), as measured 1 μm from the surface, and 60 ± 8 W m(-2) as measured by a 5 μm depthwise average. These threshold values agree well with control experiments and literature values based on direct irradiation with daylight. In contrast, negligible growth is observed with evanescent light penetration depths less than the minor dimension of the rod-like bacterium (achieved at larger light incident angles). Collectively these results indicate that evanescent light waves can be used to tailor and direct light into cyanobacteria, driving photosynthesis.
Authors:
Matthew D Ooms; Vincent J Sieben; Scott C Pierobon; Erica E Jung; Michael Kalontarov; David Erickson; David Sinton
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-3-6
Journal Detail:
Title:  Physical chemistry chemical physics : PCCP     Volume:  -     ISSN:  1463-9084     ISO Abbreviation:  -     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-3-7     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100888160     Medline TA:  Phys Chem Chem Phys     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, CanadaM5S 1A1. sinton@mie.utoronto.ca.
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