TY - JOUR
T1 - Inactivation of photosynthetic electron flow during desiccation of desert biological sand crusts and Microcoleus sp.-enriched isolates
AU - Ohad, Itzhak
AU - Nevo, Reinat
AU - Brumfeld, Vlad
AU - Reich, Ziv
AU - Tsur, Tom
AU - Yair, Michael
AU - Kaplan, Aaron
PY - 2005/11/23
Y1 - 2005/11/23
N2 - Filamentous cyanobacteria, the main primary producers in biological sand crusts, survive harsh environmental conditions including diurnal desiccation/rehydration cycles. Here we describe the inactivation of photosystem II during dehydration of native crusts (NC) and Microcoleus sp. isolates grown on nitrocellulose filters (NCF). The morphology of NCF cells, visualized by scanning-transmission and atomic-force microscopy, disclosed long bacterial filaments encapsulated in extracellular polysaccharides (EPS) tubes consisting of parallel fibrils (100–400 nm wide and 50–100 nm high) oriented mostly perpendicular to the tube length. Presence of empty EPS tubes indicated a gliding capability of the cells. Desiccation of NC resulted in a rapid decline of Fo and complete loss of Fv. These changes were accompanied by a decrease of 77 K PSII fluorescence emission relative to that of PSI, when excited at 430 nm, and a significant decrease of energy transfer from phycobilisomes to PSII. Lowering the turgor pressure through the addition of 1.5 M trehalose to natural crusts, reduced Fv/Fm by over 50% and was accompanied by a decrease of 77 K PSI fluorescence induced by chlorophyll excitation. Excitation of phycobilisomes resulted in a downshift of the PSI emission wavelength by 8 nm, indicative of reduced energy transfer from LHCI to the core PSI. Decline of Fv/Fm in trehalose-incubated NCF cells did not induce significant changes in 77 K fluorescence emission. These results suggest that alterations in energy transfer from antennae to reaction centers may be part of the survival strategy of Microcoleus.
AB - Filamentous cyanobacteria, the main primary producers in biological sand crusts, survive harsh environmental conditions including diurnal desiccation/rehydration cycles. Here we describe the inactivation of photosystem II during dehydration of native crusts (NC) and Microcoleus sp. isolates grown on nitrocellulose filters (NCF). The morphology of NCF cells, visualized by scanning-transmission and atomic-force microscopy, disclosed long bacterial filaments encapsulated in extracellular polysaccharides (EPS) tubes consisting of parallel fibrils (100–400 nm wide and 50–100 nm high) oriented mostly perpendicular to the tube length. Presence of empty EPS tubes indicated a gliding capability of the cells. Desiccation of NC resulted in a rapid decline of Fo and complete loss of Fv. These changes were accompanied by a decrease of 77 K PSII fluorescence emission relative to that of PSI, when excited at 430 nm, and a significant decrease of energy transfer from phycobilisomes to PSII. Lowering the turgor pressure through the addition of 1.5 M trehalose to natural crusts, reduced Fv/Fm by over 50% and was accompanied by a decrease of 77 K PSI fluorescence induced by chlorophyll excitation. Excitation of phycobilisomes resulted in a downshift of the PSI emission wavelength by 8 nm, indicative of reduced energy transfer from LHCI to the core PSI. Decline of Fv/Fm in trehalose-incubated NCF cells did not induce significant changes in 77 K fluorescence emission. These results suggest that alterations in energy transfer from antennae to reaction centers may be part of the survival strategy of Microcoleus.
UR - http://www.scopus.com/inward/record.url?scp=29144453420&partnerID=8YFLogxK
U2 - 10.1039/b506300k
DO - 10.1039/b506300k
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C2 - 16307110
AN - SCOPUS:29144453420
SN - 1474-905X
VL - 4
SP - 977
EP - 982
JO - Photochemical and Photobiological Sciences
JF - Photochemical and Photobiological Sciences
IS - 12
ER -