Genetic and physiological characterization of an H. jecorina xdh1 deletion mutant. (A) Southern analysis of xdh1 deletion strains. Genomic DNA was digested with EcoRV and probed with a 2.5-kb SacII fragment of xdh1. Replacement of the xdh1 coding region by the hygromycin resistance-conferring expression cassette in the xdh1 deletion strain leads to an ∼900-bp increase in the size of the 10-kb hybridizing fragment in strain QM9414 to ∼11 kb in the xdh1 deletion strain. (B) Comparison of the growth behaviors of parent strain QM9414 and the xdh1 deletion strain on plates containing d-glucose (Glc), d-xylose (Xyl), xylitol (Xol), l-arabinose (Ara), and l-arabinitol (Aol) as carbon sources. (C) Effect of the xdh1 deletion on biomass production during growth on various carbon sources in shake flasks. QM, QM9414. (D) Microscopic views of strains QM9414 and ΔXDH1 grown on d-xylose.