title: Prolonged incubation with low concentrations of mercury alters energy transfer and chlorophyll (Chl) a protein complexes in Synechococcus 6301: changes in Chl a absorption and emission characteristics and loss of the F695 emission band.
abstract: Synechococcus PCC 6301 cells grown in the presence of low sublethal levels of (about 2 microM) mercury induced alterations in chlorophyll (Chl) a absorption without significant alterations in phycocyanin. Chl a fluorescence emission in Hg(2+)-raised cells showed a large (about 18 nm) blue shift in the peak emission. No major spectral changes in phycobilisome (PBsome) emission characteristic were noticed, indicating major structural alterations in Chl-protein complexes by incubation with Hg2+ ions. Low temperature (77K) emission spectra of cells grown in the presence of Hg2+ showed a loss of the characteristic Chl a emission band at 695 nm (F695), which is known to be linked to photosystem II photochemistry and to originate from the Chl a of core antenna polypeptide CP 47 of photosystem II. The SDS-PAGE polypeptide profile of thylakoids indicates a loss of a polypeptide(s) with a molecular mass between 40 and 60 kDa by Hg2+ incubation of cells. Our results suggest that prolonged incubation of Synechococcus 6301 cells with low concentrations of Hg2+ affects the Chl a spectral properties and the structure of Chl-protein complexes.
authors.affiliation: Bioenergetics and Photobiochemistry Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
authors.forename: S D
authors.initials: SD
authors.lastname: Murthy
authors.forename: N
authors.initials: N
authors.lastname: Mohanty
authors.forename: P
authors.initials: P
authors.lastname: Mohanty
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D000458:Cyanobacteria / Q000187:drug effects* / Q000378:metabolism*; D004735:Energy Transfer / Q000187:drug effects; D008628:Mercury / Q000008:administration & dosage / Q000633:toxicity*; D010788:Photosynthesis / Q000187:drug effects; D045524:Phycobilisomes; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
chemical_list: D045524:Phycobilisomes; D002734:Chlorophyll; D008628:Mercury; D000077194:Chlorophyll A