{{Short description|Genus of cyanobacteria}} {{Automatic taxobox |taxon=Rippkaea |authority=J.R.Johansen & Mareš 2019 |subdivision_ranks=Species |subdivision= * ''R. orientalis'' <small>J.R.Johansen & Mareš 2019</small> (type species)

(see text) |synonyms= None

'''Species synonyms''' * ''R. orientalis'' ** ''Cyanothece'' PCC 8801 = ''Synechococcus'' sp. Rf-1 ** ''Cyanothece'' PCC 8802 }}

'''''Rippkaea''''' is a genus of unicellular cyanobacteria in the family Microcystaceae or Aphanothecaceae. The genus was circumscribed in 2019 by J.R. Johansen and Mareš, with ''Rippkaea orientalis'' as the type species. Prior to that the genus was treated as ''Cyanothece'' or ''Synechococcus'' on morphological grounds, which has proven inadequate in light of molecular data.<ref name=JM19>{{cite journal|last1=Mareš |first1=Jan |last2=Johansen |first2=Jeffrey R. |last3=Hauer |first3=Tomáš |last4=Zima |first4=Jan |last5=Ventura |first5=Stefano |last6=Cuzman |first6=Oana |last7=Tiribilli |first7=Bruno |last8=Kaštovský |first8=Jan |last9=Collier |first9=J. |title=Taxonomic resolution of the genus ''Cyanothece'' (Chroococcales, Cyanobacteria), with a treatment on ''Gloeothece'' and three new genera, ''Crocosphaera, Rippkaea'' , and ''Zehria'' |journal=Journal of Phycology |date=2019 |volume=55 |issue=3 |pages=578–610 |doi=10.1111/jpy.12853 |pmid=30830691 |bibcode=2019JPcgy..55..578M }}</ref>

== Etymology == The genus name ''Rippkaea'' is in honour of Rosmarie Rippka, "a prominent cyanobacterial researcher who ushered in the period of using strains to study cyanobacteria".<ref name=JM19/>

== Description == The two PCC strains are free-living, unicellular cyanobacteria isolated from rice fields in Taiwan. Cells are oval to circuclar and divide by simple binary fission. Thyalkoids are arranged in parallel bundles crossing the entire cell. Formation of mucilaginous colonies is only occasional.<ref name=JM19/>

The genus is able to fix nitrogen. It has a circadian rhythm governing photosynthesis, nitrogenase activity, and animo acid uptake.<ref>{{cite book|last1=Williams |first1=Stanly B. |title=A Circadian Timing Mechanism in the Cyanobacteria |series=Advances in Microbial Physiology |date=2006 |volume=52 |pages=229–296 |doi=10.1016/S0065-2911(06)52004-1 |pmid=17027373 |isbn=978-0-12-027752-0 }}</ref>

=== Endosymbiosis === This genus (sensu GTDB)<ref>{{cite web |title=GTDB - GCF_003574135.1 |url=https://gtdb.ecogenomic.org/genome?gid=GCF_003574135.1 |website=gtdb.ecogenomic.org}}</ref> includes a number of diazoplasts, the intracellular nitrogen-fixing endosymbionts of certain ''Epithemia'' diatoms. These endosymbionts have lost the ability to photosynthesize, relying on their host for organic carbon, while providing fixed nitrogen in return.<ref name="PE">{{cite journal |last1=Moulin |first1=SLY |last2=Frail |first2=S |last3=Braukmann |first3=T |last4=Doenier |first4=J |last5=Steele-Ogus |first5=M |last6=Marks |first6=JC |last7=Mills |first7=MM |last8=Yeh |first8=E |title=The endosymbiont of Epithemia clementina is specialized for nitrogen fixation within a photosynthetic eukaryote. |journal=ISME Communications |date=January 2024 |volume=4 |issue=1 |article-number=ycae055 |doi=10.1093/ismeco/ycae055 |pmid=38707843 |pmc=11070190 }}</ref>

== Phylogeny == Phylogeny per GTDB Release 10-RS226 (April 2025). Provisional names are preserved.<ref>{{cite web|title=bac120_r226.sp_labels.tree|url=https://data.gtdb.aau.ecogenomic.org/releases/release226/226.0/auxillary_files/bac120_r226.sp_labels.tree}}</ref>

Mapping from provisional names of diazoplasts to published names of ''Epithemia'' hosts is obtained as follows: the associated NCBI genome assembly records is queried based on the GTDB genome IDs (e.g. GCF_003574135.1) and the host species name is found from the linked publication or BioSample metadata.

{{clade |sublabel1=99 |1={{clade |sublabel1=100 |1={{clade |sublabel1=80 |1={{clade |sublabel1=100 |1={{clade |1=''Crocosphaera'' |2=''Atelocyanobacterium'' }} |2=JBCDDV01 sp039180145 }} |2=UHCC-0190 }} |2=''Aphanothece_B sacrum'' }} |sublabel2=100|label2=''Rippkaea'' |2={{clade |sublabel1=100 |1={{clade |sublabel1=100 |label1=Diazoplasts |1={{clade |sublabel1=99 |1={{clade |sublabel1=70 |1={{clade |1=''R.'' sp000829235<br />''E. turgida'' symbioant |2=''R.'' sp003574135<br />''E. gibberula'' symbioant }} |2=''R.'' sp029919255<br />''E. clementina'' symbioant }} |2=''R.'' sp947331815<br />''E. pelagica'' symbioant }} |2=''R.'' sp002110465 }} |sublabel2=100 |2={{clade |1=''R. orientalis'' |2=''R.'' sp003448685 }} }} }}

== References == {{Reflist}}

{{Taxonbar|from=Q124154411}} {{Authority control}}

Category:Chroococcales Category:Cyanobacteria genera Category:Taxa described in 2019