Editing Endolith (section)

==Metabolism and survival==
The metabolism of endolithic microorganisms is versatile; there have been found genes involved in [[Sulfur metabolism|sulphur metabolism]],  [[iron-oxidizing bacteria|iron metabolism]] and [[carbon fixation]] in many endolithic communities. Whether they metabolize directly from the surrounding rock, or excrete an acid to dissolve it first is yet undetermined. According to Meslier & DiRuggiero <ref name="Academic press">{{cite book |first1=V |last1=Meslier |first2=J |last2=DiRuggiero |year=2019 |chapter=7 Endolithic microbial communities as model systems for ecology and astrobiology |editor1-last=Seckbach |editor1-first=J. |editor2-last=Rampelotto |editor2-first=P.H. |title=Model Ecosystems in Extreme Environments |publisher=Academic press | isbn= 978-0-1281-2742-1}}</ref> there are genes found in the endolithic community involved in [[nitrogen fixation]]. The [[Ocean Drilling Program]] found microscopic trails in [[basalt]] from the [[Atlantic Ocean|Atlantic]], [[Indian Ocean|Indian]], and [[Pacific Ocean|Pacific]] oceans that contain [[DNA]].<ref name="glass munchers">{{cite web|last1=Mullen|first1=Leslie|title=Glass Munchers Under the Sea|url=http://www.nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=98|website=NASA Astrobiology Institute|url-status=dead|archive-url=https://web.archive.org/web/20130220141852/http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=98|archive-date=20 February 2013}}</ref><ref name="basalt">{{cite journal|last1=Lysnes|first1=Kristine|last2=Torsvik|first2=Terje|last3=Thorseth|first3=Ingunn H.|last4=Pedersen|first4=Rolf B.|title=Microbial Populations in Ocean Floor Basalt: Results from ODP Leg 187|journal=Proc ODP Sci Results|series=Proceedings of the Ocean Drilling Program|date=2004|volume=187|pages=1–27|url=http://www-odp.tamu.edu/publications/187_SR/VOLUME/CHAPTERS/203.PDF|doi=10.2973/odp.proc.sr.187.203.2004 }}</ref> Photosynthetic endoliths have also been discovered.<ref name="photendolith">{{cite journal |last1=Wierzchos |first1=Jacek |last2=Ascaso |first2=Carmen |last3=McKay |first3=Christopher P. |title=Endolithic Cyanobacteria in Halite Rocks from the Hyperarid Core of the Atacama Desert |journal=Astrobiology |date=2006 |volume=6 |issue=3 |pages=415–422 |doi=10.1089/ast.2006.6.415|pmid=16805697 |bibcode=2006AsBio...6..415W |hdl=10261/19099 |hdl-access=free }}</ref>

As water and nutrients are sparse in the endolith's surrounding environment, water limitation is a key factor in the capacity of survival of many endolithic microorganisms. Many of those microorganisms have adaptations to survive in low concentrations of water.<ref name="Academic press"/> Additionally, the presence of pigments, especially in [[cyanobacteria]] and some [[algae]], such as; [[Β-Carotene|beta carotenes]] and [[chlorophyll]] help them to protect against dangerous radiation and act as a way to obtain energy.<ref>{{cite journal |last1=Osterrothová |first1=K |last2=Culka |first2=A |last3=Němečková |first3=K |last4=Kaftan |first4=D |last5=Nedbalová |first5=L |last6=Procházková |first6=L |last7=Jehlička |first7=J |title=Analyzing carotenoids of snow algae by Raman microspectroscopy and high-performance liquid chromatography |journal=Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy |date=2019 |volume=212 |pages=262–271 |doi=10.1016/j.saa.2019.01.013|pmid=30658280 |bibcode=2019AcSpA.212..262O |s2cid=58604046 }}</ref> Another characteristic is the presence of a very slow [[reproduction]] cycle. Early data suggest some only engage in [[cell division]] once every hundred years. In August 2013, researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years.<ref>{{cite web|last1=Yirka|first1=Bob|title=Soil beneath ocean found to harbor long-lived bacteria, fungi and viruses|url=http://phys.org/news/2013-08-soil-beneath-ocean-harbor-bacteria.html|website=Phys.org|date=29 August 2013|archive-url=https://web.archive.org/web/20151029144045/http://phys.org/news/2013-08-soil-beneath-ocean-harbor-bacteria.html|archive-date=29 October 2015|url-status=live}}</ref>  Most of their energy is spent repairing [[cell damage]] caused by [[cosmic ray]]s or [[racemization]], and very little is available for reproduction or growth. It is thought that they weather long [[ice age]]s in this fashion, emerging when the temperature in the area warms.<ref name="hively"/>