Weinstein P P
Department of Biological Sciences, University of Notre Dame, Indiana 46556, USA.
J Parasitol. 1996 Feb;82(1):1-6.
Bacteria in rat feces cultures that had synthesized vitamin B12 were ingested by the free-living stages of Nippostrongylus brasiliensis and the vitamin was concentrated and stored in the third-stage infective filariform larvae. As assayed with Ochromonas malhamensis, the vitamin B12 content of a single filariform larva as well as the concentration expressed as microgram B12 per g filariform larvae reached extraordinarily high levels, the latter being the highest yet recorded for a metazoan organism. The stored B12 content of the filariforms surviving in fecal culture for as long as 104 days remained constant, whereas the B12 concentration rose due to gradual loss of larval body weight. This storage strategy ensured that a high level of the vitamin would be immediately available to the rapidly growing and differentiating worms following infection of the rat. The changing patterns of B12 content and concentration during the parasitic cycle were followed quantitatively and correlated with B12 turnover, increase in worm weight with growth, and incorporation of B12 into the eggs. The possible sources of B12 and its metabolic functions in nematodes are discussed.
合成维生素B12的大鼠粪便培养物中的细菌被巴西日圆线虫的自由生活阶段摄取，维生素在第三期感染性丝状幼虫中浓缩并储存。用马尔姆奥氏双鞭毛虫测定，单个丝状幼虫的维生素B12含量以及以每克丝状幼虫微克B12表示的浓度达到了极高水平，后者是后生动物中迄今记录到的最高水平。在粪便培养物中存活长达104天的丝状幼虫的储存B12含量保持不变，而B12浓度因幼虫体重逐渐减轻而上升。这种储存策略确保了在大鼠感染后，快速生长和分化的蠕虫能够立即获得高水平的维生素。对寄生周期中B12含量和浓度的变化模式进行了定量跟踪，并与B12周转、蠕虫体重随生长增加以及B12掺入卵中相关联。讨论了线虫中B12的可能来源及其代谢功能。
