FIGURE 4.

(A) Spectral counts (means ± SE; n = 4) of differentially expressed long-chain alkane transport proteins during growth on a medium-chain alkane (n-C₁₄,), a long-chain alkane (n-C₂₈,) and a non-hydrocarbon control (Tween 80) in Thalassolituus oleivorans MIL-1. ^∗ denotes spectral counts significantly greater (P < 0.05) during growth on n-C₂₈ relative to growth on n-C₁₄ and TW. (B) Proposed uptake of a long chain n-alkane by the identified proteins. TonB interacts with TOL_0244 which carries out high-affinity binding and energy dependent uptake of the substrate into the periplasm. In the absence of TonB, the receptor will bind the substrate but not carry out active transport. TOL_1625 is a FadL homolog which allows hydrophobic compounds to cross the cell membrane through diffusion. TOL_3188 is a porin which may facilitate passive uptake of long-chain alkanes and may be transported to the outer membrane by the inner-membrane transport protein TOL_3187.