David Grayless<p>Bacteria ( ; sg.: <a href="https://mastodon.social/tags/bacterium" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>bacterium</span></a>) are ubiquitous, mostly free-living organisms often consisting of one <a href="https://mastodon.social/tags/biologicalCell" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>biologicalCell</span></a>. They constitute a large <a href="https://mastodon.social/tags/domain" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>domain</span></a> of <a href="https://mastodon.social/tags/prokaryotic" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>prokaryotic</span></a> <a href="https://mastodon.social/tags/microorganisms" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>microorganisms</span></a>. Typically a few <a href="https://mastodon.social/tags/micrometres" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>micrometres</span></a> in length, bacteria were among the first life forms to appear on Earth, and are present in most of its <a href="https://mastodon.social/tags/habitats" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>habitats</span></a>. Bacteria inhabit the air, soil, water, <a href="https://mastodon.social/tags/acidicHotSprings" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>acidicHotSprings</span></a>, <a href="https://mastodon.social/tags/radioactiveWaste" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>radioactiveWaste</span></a>, and the <a href="https://mastodon.social/tags/deepBiosphere" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>deepBiosphere</span></a> of <a href="https://mastodon.social/tags/EarthsCrust" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>EarthsCrust</span></a>.</p>