Cyanidiophyceae

{{Short description|Class of algae}}

{{Automatic taxobox

| image = Cyanidium O5A.jpg

| image_caption = Cyanidium sp.

| taxon = Cyanidiales

| authority = T.Christensen

| subdivision_ranks = Families

| subdivision =

• Cyanidiaceae
• Galdieriaceae

}}

Cyanidiophyceae is a class of unicellular red algae within subdivision Cyanidiophytina, and contain a single plastid, one to three mitochondria, a nucleus, a vacuole, and floridean starch.{{cite book |first1=Joseph|last1=Seckbach |first2=David J.|last2=Chapman |title=Red Algae in the Genomic Age |url=https://books.google.com/books?id=fegCa9G-c90C&pg=PA250 |access-date=31 January 2011 |date=30 August 2010 |publisher=Springer |isbn=978-90-481-3794-7 |page=250}} Pyrenoids are absent.{{cite journal | url=https://www.sciencedirect.com/science/article/pii/S0167488921000033 | doi=10.1016/j.bbamcr.2021.118949 | title=Pyrenoids: CO2-fixing phase separated liquid organelles | journal=Biochimica et Biophysica Acta (BBA) - Molecular Cell Research | date=April 2021 | volume=1868 | issue=5 | last1=Barrett | first1=James | last2=Girr | first2=Philipp | last3=MacKinder | first3=Luke C. M. | pmid=33421532 }} Most are extremophiles inhabiting acid hot springs with a pH between 0,2 and 4 and temperatures up to 56 °C.AlgaeBase Taxonomy Browser: [https://www.algaebase.org/browse/taxonomy/?id=4553 Cyanidiales] They originated in extreme environments with high temperatures and low pH, which allowed them to occupy ecological niches without any competition.{{cite book | url=https://books.google.com/books?id=rHRJDwAAQBAJ&dq=Cyanidiales+empty+niche+cyanobacteria+pH+5&pg=PA105 | title=Phycology | isbn=978-1-107-55565-5 | last1=Lee | first1=Robert Edward | date=2018 | publisher=Cambridge University Press }}

While still found in extreme environments, they have also adapted to live along streams, in fissures in rock walls and in soil, but usually prefer relatively high temperatures. They have never been found in basic freshwater or seawater habitats.{{cite book | url=https://books.google.com/books?id=itJKDwAAQBAJ&dq=Cyanidiophyceae+freshwater+seawater&pg=PA82 | title=Microalgae in Health and Disease Prevention | isbn=978-0-12-811406-3 | last1=Levine | first1=Ira A. | last2=Fleurence | first2=Joël | date=2018 | publisher=Academic Press }} The main photosynthetic pigment is C-phycocyanin. Except for Galdieria partita, which can reproduce sexually,{{cite journal |first1=Shunsuke |last1=Hirooka |first2=Takeshi |last2=Itabashi |first3=Takako M |last3=Ichinose |first4=Ryo |last4=Onuma |first5=Takayuki |last5=Fujiwara |first6=Shota |last6=Yamashita |first7=Lin Wei |last7=Jong |first8=Reiko |last8=Tomita |first9=Atsuko H |last9=Iwane |first10=Shin-ya |last10=Miyagishima |pmid=36194630 |journal=Proc Natl Acad Sci U S A |year=2022 |volume=119 |issue=41 |pages=e2210665119 |doi=10.1073/pnas.2210665119|pmc=9565259 |title=Life cycle and functional genomics of the unicellular red alga Galdieria for elucidating algal and plant evolution and industrial use|doi-access=free |bibcode=2022PNAS..11910665H }} reproduction is asexual by binary fission or formation of endospores.{{cite journal |last1=Yoon|first1=Hwan Su |last2=Muller|first2=Kirsten M. |last3=Sheath|first3=Robert G. |last4=Ott|first4=Franklyn D. |last5=Bhattacharya|first5=Debashish |title=Defining the Major Lineages of Red Algae (Rhodophyta)1 |journal=Journal of Phycology |date=April 2006 |volume=42 |issue=2 |pages=482–492 |doi=10.1111/j.1529-8817.2006.00210.x |bibcode=2006JPcgy..42..482Y |s2cid=27377549}} The group, consisting of a single order (Cyanidiales), split off from the other red algae more than a billion years ago. Three families, four genera, and nine species are known, but the total number of species is probably higher. They are primarily photoautotrophic, but heterotrophic and mixotrophic growth also occurs. After the first massive gene loss in the common ancestor of all red algae, where ca. 25% of the genes were lost, a second gene loss occurred in the ancestor of Cyanidiophyceae, where additional 18% of the genes were lost.{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S108495212200074X | doi=10.1016/j.semcdb.2022.03.007 | title=Extremophilic red algae as models for understanding adaptation to hostile environments and the evolution of eukaryotic life on the early earth | date=2023 | last1=Van Etten | first1=Julia | last2=Cho | first2=Chung Hyun | last3=Yoon | first3=Hwan Su | last4=Bhattacharya | first4=Debashish | journal=Seminars in Cell & Developmental Biology | volume=134 | pages=4–13 | pmid=35339358 | doi-access=free }} Since then, some gene gains and minor gene losses have taken place independently in the Cyanidiaceae and Galdieriaceae, leading to genetic diversification between the two groups, with Galdieriaceae occupying more diverse and varied niches in extreme environments than Cyanidiaceae.{{cite journal |last1=Cho |first1=Chung Hyun |last2=Park |first2=Seung In |last3=Huang |first3=Tzu-Yen |last4=Lee |first4=Yongsung |last5=Ciniglia |first5=Claudia |last6=Yadavalli |first6=Hari Chandana |last7=Yang |first7=Seong Wook |last8=Bhattacharya |first8=Debashish |last9=Yoon |first9=Hwan Su |year=2023 |title=Genome-wide signatures of adaptation to extreme environments in red algae |journal=Nature Communications |volume=14 |issue=1 |page=10 |doi=10.1038/s41467-022-35566-x |pmid=36599855 |pmc=9812998 |bibcode=2023NatCo..14...10C }}