@article {Rocap2002,
	title = {Resolution of Prochlorococcus and Synechococcus ecotypes by using 16S-23S ribosomal DNA internal transcribed spacer sequences},
	journal = {Applied and Environmental Microbiology},
	volume = {68},
	number = {3},
	year = {2002},
	note = {tex.mendeley-tags: RCC,rcc},
	pages = {1180{\textendash}1191},
	abstract = {Cultured isolates of the marine cyanobacteria Prochlorococcus and Synechococcus vary widely in their pigment compositions and growth responses to light and nutrients, yet show greater than 96\% identity in their 16S ribosomal DNA (rDNA) sequences. In order to better define the genetic variation that accompanies their physiological diversity, sequences for the 16S-23S rDNA internal transcribed spacer (ITS) region were determined in 32 Prochlorococcus isolates and 25 Synechococcus isolates from around the globe. Each strain examined yielded one ITS sequence that contained two tRNA genes. Dramatic variations in the length and G+C content of the spacer were observed among the strains, particularly among Prochlorococcus strains. Secondary-structure models of the ITS were predicted in order to facilitate alignment of the sequences for phylogenetic analyses. The previously observed division of Prochlorococcus into two ecotypes (called high and low-B/A after their differences in chlorophyll content) were supported, as was the subdivision of the high-B/A ecotype into four genetically distinct clades. ITS-based phylogenies partitioned marine cluster A Synechococcus into six clades, three of which can be associated with a particular phenotype (motility, chromatic adaptation, and lack of phycourobilin). The pattern of sequence divergence within and between clades is suggestive of a mode of evolution driven by adaptive sweeps and implies that each clade represents an ecologically distinct population. Furthermore, many of the clades consist of strains isolated from disparate regions of the world{\textquoteright}s oceans, implying that they are geographically widely distributed. These results provide further evidence that natural populations of Prochlorococcus and Synechococcus consist of multiple coexisting ecotypes, genetically closely related but physiologically distinct, which may vary in relative abundance with changing environmental conditions.},
	keywords = {Divinyl Chlorophyll a, genetic diversity, Marine Cyanobacterium Synechococcus, Multiple Evolutionary Origins, North Atlantic, Nucleotide Sequence, rcc, Region, Rna Operon, sargasso sea, Water Column},
	doi = {10.1128/AEM.68.3.1180-1191.2002},
	author = {Rocap, G and Distel, D L and Waterbury, J B and Chisholm, S W}
}
@article {Jacquet2001,
	title = {Cell cycle regulation by light in Prochlorococcus strains},
	journal = {Applied and Environmental Microbiology},
	volume = {67},
	number = {2},
	year = {2001},
	note = {tex.mendeley-tags: RCC,rcc},
	pages = {782{\textendash}790},
	abstract = {<p>The effect of light on the synchronization of cell cycling was investigated in several strains of the oceanic photosynthetic prokaryote Prochlorococcus using flow cytometry. When exposed to a light-dark (L-D) cycle with an irradiance of 25 mu mol of quanta m(-2) s(-1), the low-light-adapted strain SS 120 appeared to be better synchronized than the high-light-adapted strain PCC 9511. Submitting LD-entrained populations to shifts (advances or delays) in the timing of the "light on" signal translated to corresponding shifts in the initiation of the S phase, suggesting that this signal is a key parameter for the synchronization of population cell cycles. Cultures that were shifted from an L-D cycle to continuous irradiance showed persistent diel oscillations of flow-cytometric signals (light scatter and chlorophyll fluorescence) but with significantly reduced amplitudes and a phase shift. Complete darkness arrested most of the cells in the G(1), phase of the cell cycle, indicating that light is required to trigger the initiation of DNA replication and cell division. However, some cells also arrested in the S phase, suggesting that cell cycle controls in Prochlorococcus spp. are not as strict as in marine Synechococcus spp. Shifting Prochlorococcus cells from low to high irradiance translated quasi-instantaneously into an increase of cells in both the S and G(2) phases of the cell cycle and then into faster growth, whereas the inverse shift induced rapid slowing of the population growth rate. These data suggest a close coupling between irradiance levels and cell cycling in Prochloroeoccus spp.</p>
},
	keywords = {cyanobacteria, Equatorial Pacific, Gene Expression, Growth, Mediterranean Sea, North Atlantic, Photosynthetic Prokaryote, picoplankton, Populations, rcc, Synechococcus},
	doi = {10.1128/AEM.67.2.782-790.2001},
	author = {Jacquet, S and Partensky, F and Marie, D and Casotti, R and Vaulot, D}
}
