Our results showed the potential of wheat bran to produce laccase by white-rot fungi, because high laccase activities were obtained. However, the use of different strains
for the laccase production clearly modifies the culture conditions, especially for the close-to-the-substrate hyphae. In this region, the hyphae density and the number of layers clearly depend on the strain. On the one hand, P. ostreatus PI3K targets presented the highest hypha density and the largest number of layers in the interface structure, showing a tendency for a hair-like growing morphology. This morphology could be linked to the low oxygen diffusion presented in the inner layers. On the other hand, C. unicolor presented the lowest hypha density and the smallest number of layers in the interface structure; thus, this fungus was expected to have
the best oxygen diffusion into its inner layers. However, there is no clear relationship between fungal morphology, hypha density and laccase production. Pleurotus ostreatus produced nearly 50% more laccase per gram of total dry matter than the one produced by C. unicolor. Trametes versicolor, which presented medium hypha density, produced the highest activity of laccase per gram of total dry matter, but T. pubescens, with similar growth morphology likely related to their common genus (Trametes), produced the lowest quantity of laccase per gram of total dry matter among all the strains studied. This indicates that, although all strains presented differences in the hypha size, clump size, morphology and the number of layers in the interface structure, NU7441 concentration the laccase production in terms of activity per gram of total dry matter cannot be related to these characteristics of the culture, but directly to the strain. This is in agreement with the review by Grimm et al. (2005), which stated that no simple relationship was found between morphology and productivity in filamentous fungi. This research was financed by the Spanish Ministry of Education
and Science (Project CTQ2007-66541). We thank Tau-protein kinase Dr A. Hatakka from the Department of Food and Environmental Sciences at the University of Helsinki (Helsinki, Finland) for the Trametes versicolor K120a2 (FBCC564), Cerrena unicolor T71 (FBCC744) and Pleurotus ostreatus DSM 11191 (FBCC375) fungal strains and Erika Winquist from the Aalto University School of Science and Technology (Aalto, Finland) for her help and support reading the manuscript. “
“Here, we describe mutants of Mycoplasma pulmonis that were obtained using a minitransposon, Tn4001TF1, which actively transposes but is then unable to undergo subsequent excision events. Using Tn4001TF1, we disrupted 39 genes previously thought to be essential for growth. Thus, the number of genes required for growth has been overestimated. This study also revealed evidence of gene duplications in M.