Functional and biosynthetic interrelationships among the B vitamins are, of late, coming to light (CL~E~qON 1965). The reported (DocTo~ et al. 1953) influence of vitamin BI~ on the conversion of relic acid to citrovorum factor by chick liver enzymes, could not be located in the reduction steps leading to formation of tetrahydro pteroylgintamic acid (Ro~v~Rws and NICHoL 1962). Work reviewed by PLAVT (PLAt~T 1961) has indicated the common metabolic pathway leading to biogenesis ofpurines, pteridines, and riboflavin. In the present work an attempt has been made to assess the influence of pantothenic acid, riboflavin, vitamin B~2 and a pyrimidine, thymine, on the biosynthesis of relic acid in microorganisms. Preliminary observations arising out of this study h~ve been reported earlier (CoEL~O et al. 1962; MA~KODI and REGE 1964).
Experimental
Organisms. The organisms employed were Lactobacillus arabinosus (ATCC 8014), Escherichia cell 113-3, vitamin Bl~/methionine auxotroph, Euglena gracilis var. baciUaris, Escherichia cell 15 T-, thymine auxotroph, Streptococcus/aecalis R (ATCC 80~3) and Lactobacillus leichmannii 313. All organisms were maintained oll agar stabs or slopes of the composition, yeast extract, 0.3~ peptone, 1~ glucose, 2~ KHePOa, 0.1~ liver extract, 0.3~ and agar, 1.5~ E. gracilis was maintained by weekly transfer in the liquid medium of HV~NE~ et al. (1956).
Media. L. arabinosus was grown in the pantothenic acid assay medium (SKEGGS and WnIG~r 1944) at optimal and suboptimal levels of calcium pantothenate corresponding to 40 and 10 m~g per ml respectively. To study the effect of riboflavin, L. arabinosus was grown in the same medium devoid of any purines or pyrimidines. Riboflavin at four different levels, corresponding to 10, 50, 100 and 250 mf~g per ml was incorporated. E. coli auxotrophs were grown in a salts-dextrose medium of GnEEN and SEVAG (1946); vitamin B12 at four different levels 1.0, 2.0, 4.0 and 6.0 mgg per 100 ml in the basal medium for B~/methionine auxotroph and thymLae at optimal and suboptimal levels corresponding to 500 and 125 mgg per In/, respectively, were SUpl)lemen~ed.
Arch. Mikrobiol., Bd. 53 S