Figure 5.

O. tauri RCC745 requires ThiM to salvage B1 from thiazole-related precursor(s) provided by co-cultured bacterioplankton Marinobacter sp. OTB1 and supplemented HMP. The cell abundances of O. tauri RCC745 wild-type (Wt) and ΔThiM mutant (ΔThiM) lines are presented from day 3 of co-culture incubations without (a) or with (b) antibiotics (penicillin G and streptomycin). Bacterioplankton OTB1 growth was detectable only in co-cultures not treated with antibiotics (c). An arrow points to the lack of O. tauri RCC745 ΔThiM mutant growth in co-cultures supplemented with HMP and not treated with antibiotics (enabling bacterioplankton OTB1 cells to grow (c)). In contrast, wild-type RCC745 grew under the same co-culture conditions (a); underscoring the need for ThiM in salvaging B1 from added HMP and thiazole-related precursor(s) provided by OTB1 cells. Increased growth of the RCC745 wild-type versus ThiM mutant in (a) also suggests OTB1 cells provide precursors, not intact B1, useful for wild-type RCC745 to meet its B1 demands. Additions of B1 stimulated growth of RCC745 and ΔThiM mutant lines (a, b) confirming their B1 growth limitation and viability. Averages (columns) and s.d. (error bars) of triplicate co-cultures are presented. B1, HMP (1 nM each) and/or antibiotics were added on day 0. Negative controls (- Control) received no vitamin addition. Asterisks denote values significantly higher than respective negative controls in (a, b; t-test, n=3, P<0.05).