Prochlorococcus

Generic name: PROCHLOROCOCCUS Chisholm, Frankel, Goericke, Olson, Palenik, Waterbury, West-Johnsrud et Zettler, 1992. p. 299

Synonyms:

Diagnosis:
Etymology:

Castenholz (2001): Pro.chlo' o.coc' cus. Gr. prefix pro primitive; Gr. adj. chloros green; Gr. n. kokkos grain or kernel; M.L. masc. n. Prochlorococcus primitive green kernel (cell).

Type species: Prochlorococcus marinus Chisholm et al. 1992; holotype strain CCMP 1375 (isol. from 120 depth in Sargasso sea)

Descriptions:
Castenholz (2001): Marine planktonic cyanobacteria that possess spherical to slightly rod-shaped cells (0.5-0.8 X 0.7-1.6 um) and divide by binary fission in a single plane. They lack phycobilisomes and contain divinyl-chlorophyll a and b (a2 and b2). The members of this genus (Fig. BIO.22) range in size from 0.5 to 0.8 um in width and 1.0-1.6 um in length (predivisional cells). Although they show a superficial resemblance to various slightlv larger strains of picoplanktonic marine Ssnechococcus (see Fig. B10.24F), all isolates of Prochlorococcus are distinguished by their lack of phycobilisomes and phycobiliproteins (except small quantities of PE III in the case of strain CCMP 1375T; see Hess et al.,1999. and possibly other strains). As a light-harvesting-antenna members of the genus Prochlorococcus synthesize divinyl-chlorophyll a and b (a2 and b2) (Goericke and Repeta, 1993). Thi the principal characteristic distinguishing this genus is the replacement of phycobilisomes bv a chlorophyll a/b complex analogous to that of green algal and green plant chloroplasts. This pigment composition confers a yellow-green color to the culture.

Genotype differences, molecular data:

Reproduction strategies, life cycles, cell division:

Ultrastructure:

Taxonomic position, higher hierarchy:

Ecology, ecophysiology, ecological significance:

Physiology and biochemistry:
Castenholz (2001): Some strains of Prochlorococcus that synthesize divinyl chloro-phyll a and 6 may contain monovinyl-chlorophyll b (b2), but alwav lack monovinyl-chlorophyll a. Minor quantities of a chlorophyll f-like pigment (Mg, 3-8 divinyl phaeoporphyrin a5) and α-carotene, rather than β-carotene are additional characteristic features. Axenic strain PCC 9511 uses ammonia or urea as a nitrogen source; nitrate is not utilized (Rippka et al., 2000). Several organic phosphorus compounds efficiently replace phosphate, indicating ecto-phosphohydrolase activity.

Distribution, endemism, problematic citations:

Reference strain:
CCMP 1375 (type strain), PCC9511 (Sargasso sea)

Infrageneric scheme, species concept:

List of species:
Prochlorococcus marinus Chisholm et al. 1992
Prochlorococcus marinus subsp. pastoris Rippka et al. 2000

Keys:

List of stains:

Drawings, images:

Castenholz (2001: 507)

Application technology:

Literature:

	2.1 taxonomy: Chisholm et al. 1992, Rippka et al. 2000, Urbach et al. 1992
	2.2 cytomorphology:
	2.3 16S rRNA sequencing: Urbach et al. 1992, Wilmotte & Herdman 2001
	2.4 biology and life cycles: Goericke & Repeta 1993, Rippka et al. 2000
	2.5 ecology: Partensky et al. 1993, Partensky et al. 1999

Back to list of valid genera

Navigation