Wikipedia:Reference desk/Archives/Science/2018 December 29

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December 29

Biochemistry factors

Haemophilus influenzae requires X and V factors for growth. In this culture, Haemophilus has only grown around the paper disc that has been impregnated with X and V factors. No bacterial growth is seen around the discs that only contain either X or V factor.

The image and caption are copied from the Haemophilus influenzae article. The body of the article has comparatively little information: it says Bacterial culture of H. influenzae is performed on agar plates, the preferable one being chocolate agar, with added X (hemin) and V (nicotinamide adenine dinucleotide) factors at 37 °C in a CO₂-enriched incubator, but neither hemin nor NAD appears elsewhere in the article. In this context, what is a factor, what do these chemicals do in their roles as X and V factors, and in general what are X and V factors? I see from the NAD article that it's a Cofactor (biochemistry), but we don't have a Factor (biochemistry) article. I tried X factor, but that's a TV show, and X Factor (disambiguation) doesn't have anything relevant, while V factor doesn't exist. (I get a sense of NAD's general activities from its article, but I'm not clear if its redox activities make it a factor, or if it's something else.) If I've missed an answer that's provided in a linked article, this is probably because I don't have much chemistry background and didn't understand something crucial. Nyttend (talk) 05:38, 29 December 2018 (UTC)

PS, I found Factor X and Factor V, but neither hemin nor nicotinamide appears in either one of them, and it looks like they're related to the clotting process in blood; I didn't see anything seemingly relevant to unicellular organisms. There is no Factor W or W Factor article, and W factor began This theory about time travel is correct and uses logic that is being constantly proven... Nyttend (talk) 05:43, 29 December 2018 (UTC)

I went to PubMed and searched "factor X" hemophilus and found nine papers, the earliest of which is [1]. Because this is an exercise in psychoanalyzing the person who came up with the name rather than science per se, there might really be no alternative to know for sure but to go back and get the German paper and see what its references were or if it named the factors itself. But one of the other references might let the reason slip. That said, I would make a wager that X and V are Roman numerals. Probably one thing and another were isolated and named in numerical (Roman) order as things that seemed to help the growth rate, then on rescreening maybe some of them didn't pan out or turned out to be the same thing in different forms or whatever, until they got down to two "essential" things, both of which could be supplied from catalase [2] though without reading I don't know if that happens always never or somewhere in between. (You should see from this idea though how the number of factors could vary, especially in early days of research)

Cofactors, in general, are things proteins rely on to "help" their activity. The individual protein made by some gene (or made of polypeptide protein subunits each made by a gene if you want to be anal about it) would be the "factor", and then the "cofactor" is what is needed so the factor works. Typically, modern biology seems to find that proteins work well for most things, but whenever you run across something really ancient and important, that's when "RNA world" hangovers tend to turn up. So like ribosomes are made out of RNA decorated with proteins, and in this case, proteins have prosthetic groups (another term for cofactor, apparently implying that the protein with its 21 amino acid choices + modifications is "crippled" and needs help to do things). Really, something like NADH with its 5'-5' linkage and odd nucleotide base structure looks like it might be a relic from an era before DNA and RNA were standardized, let alone cells, but it is hard to think of a way to prove or disprove any such idea. Wnt (talk) 15:16, 29 December 2018 (UTC)

The relevant paper is "Studies on Bacterial Nutrition: II. Growth Accessory Substances in the Cultivation of Hemophilic Bacilli (June 1921)" and can be found here [3]. "V factor" was so-called for behaving like the (newly discovered!) vitamins, and "X factor" was simply poorly understood. Choess (talk) 03:16, 30 December 2018 (UTC)

How much time does it take for a bacterium to produce 1 ng of botulinum toxin

Couldn't find any reliable information on this simple factum here or elsewhere online.--TMCk (talk) 22:05, 29 December 2018 (UTC)

It will depend on which bacterium and which botulinum toxin, but to get started, I'll just use the number our article has in the infobox ( 149,321 g/mol ) as a molecular weight. Calculating

(1 ng) * (1 g / 10^9 ng) * ( 1 mol / 1.49321 x 10^5 g ) * (6.022 x 10^23 molecules / 1 mol) = 4.03 x 10^9 molecules. So you're asking how long it takes for a bacterium to make 4 billion molecules of botulinum toxin. My guess is that an individual bacterium won't make that many; but if you can use multiple bacteria, it should be trivial to have a few billion of them (advertently or not). So I'm not quite sure how to answer that one. Also, I didn't quickly find the "protein copy number" per bacterium looking as I intended, because all I get is people who care how many it takes per human cell to do something bad. Let us know which way you want to go from here. Wnt (talk) 04:56, 30 December 2018 (UTC)

I looked at a bunch of the original (late 1920s) reports of the isolation and analysis of the toxin from cultures. While they report yields and concentrations of the product, and the time and other incubation parameters, they don't seem to report the starting or ending colony size. DMacks (talk) 17:32, 30 December 2018 (UTC)