How to transfer chroococcidiopsis for agarized media to liquid?
Answers
Received 2 October 2000/Accepted 11 January 2001
The coccoid cyanobacterium Chroococcidiopsis dominates microbial communities in the most extreme arid
hot and cold deserts. These communities withstand constraints that result from multiple cycles of drying and
wetting and/or prolonged desiccation, through mechanisms which remain poorly understood. Here we describe
the first system for genetic manipulation of Chroococcidiopsis. Plasmids pDUCA7 and pRL489, based on the
pDU1 replicon of Nostoc sp. strain PCC 7524, were transferred to different isolates of Chroococcidiopsis via
conjugation and electroporation. This report provides the first evidence that pDU1 replicons can be maintained
in cyanobacteria other than Nostoc and Anabaena. Following conjugation, both plasmids replicated in Chroococcidiopsis sp. strains 029, 057, and 123 but not in strains 171 and 584. Both plasmids were electroporated
into strains 029 and 123 but not into strains 057, 171, and 584. Expression of PpsbA-luxAB on pRL489 was
visualized through in vivo luminescence. Efficiencies of conjugative transfer for pDUCA7 and pRL489 into
Chroococcidiopsis sp. strain 029 were approximately 1022 and 1024 transconjugants per recipient cell, respectively. Conjugative transfer occurred with a lower efficiency into strains 057 and 123. Electrotransformation
efficiencies of about 1024 electrotransformants per recipient cell were achieved with strains 029 and 123, using
either pDUCA7 or pRL489. Extracellular deoxyribonucleases were associated with each of the five strains.
Phylogenetic analysis, based upon the V6 to V8 variable regions of 16S rRNA, suggests that desert strains 057,
123, 171, and 029 are distinct from the type species strain Chroococcidiopsis thermalis PCC 7203. The high
efficiency of conjugative transfer of Chroococcidiopsis sp. strain 029, from the Negev Desert, Israel, makes this
a suitable experimental strain for genetic studies on desiccation tolerance