Cyanobacteria of the Genus Prochlorothrix†

Abstract

Green cyanobacteria differ from the blue–green cyanobacteria by the possession of a chlorophyll-containing light-harvesting antenna. Three genera of the green cyanobacteria namely Acaryochloris, Prochlorococcus, and Prochloron are unicellular and inhabit marine environments. Prochlorococcus marinus attracts most attention due to its prominent role in marine primary productivity. The fourth genus Prochlorothrix is represented by the filamentous freshwater strains. Unlike the other green cyanobacteria, Prochlorothrix strains are remarkably rare: to date, living isolates have been limited to two European locations. Taking into account fluctuating blooms, morphological resemblance to Planktothrix and Pseudanabaena, and unsuccessful attempts to obtain enrichments of Prochlorothrix, the most successful strategy to search for this cyanobacterium involves PCR with environmental DNA and Prochlorothrix-specific primers. This approach has revealed a broader distribution of Prochlorothrix. Marker genes have been found in at least two additional locations. Despite of the growing evidence for naturally occurring Prochlorothrix, there are only a few cultured strains with one of them (PCC 9006) being claimed to be axenic. In multixenic cultures, Prochlorothrix is accompanied by heterotrophic bacteria indicating a consortium-type association. The genus Prochlorothrix includes two species: P. hollandica and P. scandica based on distinctions in genomic DNA, cell size, temperature optimum, and fatty acid composition of membrane lipids. In this short review the properties of cyanobacteria of the genus Prochlorothrix are described. In addition, the evolutionary scenario for green cyanobacteria is suggested taking into account their possible role in the origin of simple chloroplast.

Primary endosymbiosis and the evolution of light and oxygen sensing in photosynthetic eukaryotes

“…However, many cyanobacteria substitute chlorophyll-based systems for phycobiliproteins under iron starvation, and some cyanobacteria only possess such systems (Bibby et al, 2001; Boekema et al, 2001). The presence of chlorophyll b in ‘green cyanobacteria’ and in plants has led to the proposal that both light-harvesting systems were present in the cyanobacterium that gave rise to the modern plastid, with subsequent loss of Chl b synthesis in cyanobacteria that retain the phycobilisome (Pinevich et al, 2012). Ingesting cyanobacterial prey must have exposed predatory eukaryotes to transient changes in oxygen tension, and subsequent digestion of the cyanobacterial cell would release the tetrapyrrole pigments from the photosynthetic reaction centers and light-harvesting complexes.…”

Consortium of the ‘bichlorophyllous’ cyanobacterium Prochlorothrix hollandica and chemoheterotrophic partner bacteria: culture and metagenome‐based description

“…Anyway, P. hollandica is highly dependent on, and actually inseparable from, heterotrophic satellites (Burger‐Wiersma et al ., ; Pinevich et al ., ). The anti‐ROS function of these bacteria may be among most plausible explanations of this dependence.…”

“…Based on concerted reactivity of PSI and PSII, they utilize water as electron donor, with waste production of dioxygen, although vary in type of light‐harvesting antenna. Thus, although the membrane attached phycobilisome is a common case, unicellular genera Acaryochloris , Prochloron and Prochlorococcus as well as the filamentous genus Prochlorothrix possess membrane‐embedded chlorophyll/carotenoid/protein complexes instead (Pinevich et al ., ). The ability of radiant energy, carbon dioxide and dinitrogen assimilation, as well as adaptation to broad repertoire of environmental conditions, makes cyanobacteria the most distributed and abundant living organisms on Earth.…”

“…We continued the above efforts by using chain plating technique (routine variant of ‘dilution‐to‐extinction’ method). Noteworthy, sorting off the non‐photosynthetic satellites has invariably led to P. hollandica growth decline (Pinevich et al ., ). It is also noteworthy that an axenic culture of P. hollandica was reported only once (Schyns et al ., ).…”

Antitumor Activity of Hierridin B, a Cyanobacterial Secondary Metabolite Found in both Filamentous and Unicellular Marine Strains

“…In fact, the findings of Shih et al [4], point out that the genomes of some reference strains included in our phylogenetic study do not contain polyketide gene clusters, such as Synechococcus sp. PCC 7335 and the filamentous cyanobacterium Prochlorothrix hollandica PCC 9006 (axenic strain, co-identical with SAG 10.89 [21]). Both of these latter strains are placed between the two sub-clades that include the hierridin B producers.…”