I heard an assertion nanobacteria exist along with some speculation about them and so on. It was news to me and got me wondering if I had missed a discovery announcement, so I ran some numbers:<\/p>\n
Consider a large nanobacteria, 30 nm by 100 nm. It has an approximate volume of 7e-23 m3<\/sup>.<\/p>\n How much DNA could this volume contain? Pop up a DNA molecule in Chime and get an estimate of dimensions: 20 bp run for 6.4 nm, so 0.32 nm \/ bp. The double helix has a radius of 1.3 nm.<\/p>\n Length of DNA with a volume equal to the cell = 7e-23 m3<\/sup> \/ [ (1.3 nm)2<\/sup> x \u00cf\u20ac ] = 1.3e-5 m A low average bacterial gene length is 300 bp, so a nanobacteria could hold a maximum of 42 kb \/ 300 bp = 139 genes. The minimum number of genes for an independent living organism is 300 – 500, so a nanobacteria can\u00e2\u20ac\u2122t have enough genes. It can\u00e2\u20ac\u2122t exist. But let\u00e2\u20ac\u2122s run the other numbers, on proteins.<\/p>\n A typical protein is 3 nm, lets call it a cube with a volume of (3 nm)3 = 2.7e-26m3<\/sup>. Now let\u00e2\u20ac\u2122s put this together and describe a nanobacteria. 30% of the volume is water and small molecules. Of the remainder, let\u00e2\u20ac\u2122s say 2\/3 is DNA and 1\/3 is protein. The nanobacteria contains enough DNA for 65 genes, and 600 proteins. Which means nanobacteria can\u00e2\u20ac\u2122t exist, they are too small. There are quite a few unlikely bits in biology (pretty much every rule in biology has exceptions), so I\u00e2\u20ac\u2122ll qualify it and say it is quite unlikely that nanobacteria exist. And to my estimates, add the evidence from projects to mass sequence DNA extracted from the environmental samples\u00e2\u20ac\u201cif nanobacteria exist, their DNA would turn up in these projects, and no new phylum of sequences has emerged.<\/p>\n An E. coli by contrast is 1 \u00c2\u00b5 x 3 \u00c2\u00b5 and can hold 600 Mb of DNA and 20 million proteins. It\u00e2\u20ac\u2122s genome is actually 4.6 Mb, and the extra space is taken up by a cell wall and protein. <\/p>\n","protected":false},"excerpt":{"rendered":" I heard an assertion nanobacteria exist along with some speculation about them and so on. It was news to me and got me wondering if I had missed a discovery announcement, so I ran some numbers: Consider a large nanobacteria, 30 nm by 100 nm. It has an approximate volume of 7e-23 m3. How much […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-18","post","type-post","status-publish","format-standard","hentry","category-estimation"],"_links":{"self":[{"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=18"}],"version-history":[{"count":0,"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=\/wp\/v2\/posts\/18\/revisions"}],"wp:attachment":[{"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jimlund.org\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nBps = length \/ bp length = 1.3e-5 m \/ 0.32 nm = 42 kb of DNA.<\/p>\n
\nA nanobacteria can hold 7e-23m3<\/sup> \/ 2.7e-26m3<\/sup> = 2600 proteins total. Low but not a hard limit on existence.<\/p>\n