Vitamin B   Some edits by  lack proper references and are factually incorrect The claim that Bacteria are the only sources of vitamin Bvitamin B is false it is produced by a unicelular alga by example Pleurochrysis Carterae httpwwwncbinlmnihgovpubmed  Fortified breakfast cereals dont offer vitamin Bvitamin B from plants they have it added as a supplement It is recommended for vegans to take supplements as such as a minimum dosage can be reliably maintained  The human gut also contains Bsynthesizing bacteria living from the mouth to the anus looks false The old  reffered study httpwwwncbinlmnihgovpubmed only reffered to small bowels and it was falsified since httpwwwbeyondvegcombillingstcompanatcompanatcshtml Claims of intestinal B production may be based on insufficient evidence Albert et al  is sometimes cited as evidence that B producing bacteria can exist in the small intestine Sometimes explicit claims are made eg that intestinal bacteria allegedly can produce adequate B Baker  and Nutrition Reviews  are related citations that comment on Albert et al  However a careful reading of Albert et al  shows that it used bacteriological assays which are of lower reliability to measure B levels Specifically the most accurate bacteriological assay they used is Ochromonas malhamensis Note that Ochromonas is the most accurate bacterial assay method for B however even it may report values for some analogues as part of its B results Schneider and Stroinski  Tables   to  pp   Herbert and Das  p  apparently regard all the bacterial assay methods as being less reliable than differential radioassay also see Herbert et al  and Herbert  for related information Additionally the data obtained in Albert et al  comes from isolated bacterial cultures Therefore it is unclear whether the bacteria would produce similar amounts of B under the conditions present in the intestines This point is discussed in Albert et al  but is sometimes ignored by dietary advocates with an ideological interest in minimizing the requirement for B in the diet The bottom line in the paper of Albert et al  is that it shows certain intestinal bacteria might produce B but it is unclear whetherhow much might be produced and absorbed under actual conditions in the small intestine  The last paragraph contain only straight propaganda from  MD personal pages contradicting the necesity of the vitamin without any reference to reliable sources  The editor was also part of a dispute on the VitaminB article httpenwikipediaorgwikiTalkVitaminBPOVissues   Preceding unsigned comment added by         Algae acquire vitamin B through a symbiotic relationship with bacteria  Individually algae and bacteria make interesting organisms to study Bacteria are organisms that can be found living in a range of different environments Besides being organisms capable of causing disease in humans they are also vital to the cycling of nutrients within the environment  Algae are organisms capable of fixing carbon through photosynthesis within aquatic systems  At the same time they are important to study because with increased nutrient loads to bodies of water can cause algal blooms which can lead to eutrophication This reduces the amount of dissolved oxygen available for use by fish and other aquatic organisms  Bacteria and algae can coexist within biofilms  Biofilms can help reduce the effects of external factors to produce areas that can allow for growth of specific bacterial populations and make conditions favorable for certain bacterially mediated processes such as denitrification   your source however didnt exactly say that B is produced by a unicelular alga It said