This study investigated how the filamentous fungus Cladosporium resinae uptakes n-alkanes, particularly dodecane, from the vapor phase. The researchers grew mycelia on various carbon sources and measured radioactive dodecane uptake using scintillation counting and autoradiography. Results showed that dodecane accumulates on the cell surface through a saturable binding process before crossing the cell membrane. Mycelia grown on dodecane exhibited the fastest uptake rates, while glucose-grown mycelia showed slower uptake. Metabolic inhibitors (formaldehyde, cyanide, azide) significantly reduced uptake rates but had smaller effects on surface partitioning, suggesting that hydrocarbon transport across the membrane involves an active process, while initial surface binding is largely passive. Higher concentrations of labeled compounds appeared at hyphal tips, possibly due to metabolic activity or wall structure differences. The fungus's lipid composition, which varies with growth substrate, appears to influence both binding affinity and uptake rates for specific alkanes.

Key findings

• Dodecane uptake by C. resinae involves two sequential steps: passive partitioning onto the cell surface (saturating at ~8 nmol/mg protein) followed by active transport across the cell membrane
• Mycelia grown on dodecane show significantly higher uptake and partitioning rates compared to mycelia grown on glucose or other n-alkanes, suggesting substrate-dependent changes in cell lipid composition enhance alkane uptake
• Metabolic inhibitors reduce intracellular uptake rates by 84% while only modestly decreasing surface partitioning, indicating active transport is required for membrane crossing
• Uptake occurs throughout the mycelium but is enhanced at hyphal tips, possibly due to less defined wall structure or higher metabolic activity in terminal cells
• The cell's lipid composition, which reflects the alkane growth substrate, plays a key role in determining both binding affinity and transport efficiency for specific alkanes