Abstract
Background: There are eighteen species within the Penicillium genus section chrysogena, including the original penicillin producers Penicillium notatum (Fleming strain) and Penicillium chrysogenum NRRL 1951. Other wild type isolates of the Penicillium genus are relevant for the production of useful proteins and primary or secondary metabolites. The aim of this article is to characterize strain specific genes and those genes which are involved in secondary metabolite biosynthesis, particularly the mutations that have been introduced during the β-lactams strain improvement programs. Results: The available genomes of several classical and novel P. chrysogenum strains have been compared. The first genome sequenced was that of the reference strain P. chrysogenum Wis54-1255, which derives from the wild type P. chrysogenum NRRL 1951; its genome size is 32.19 Mb and it encodes 12,943 proteins. Four chromosomes were resolved in P. chrysogenum and P. notatum by pulse field gel electrophoresis. The genomes of three industrial strains have a similar size but contain gene duplications and truncations; the penicillin gene cluster copy number ranges from one in the wild type to twelve in the P. chrysogenum ASP-E1 industrial strain and is organized in head to tail tandem repeats. The genomes of two new strains, P. chrysogenum KF-25, a producer of antifungal proteins isolated from a soil sample, and P. chrysogenum HKF2, a strain with carbohydrate-converting activities isolated from a sludge treatment plant, showed strain specific genes. Conclusions: The overall comparison of all available P. chrysogenum genomes indicates that there are a significant number of strain-specific genes, mutations of structural and regulatory genes, gene cluster duplications and DNA fragment translocations. This information provides important leads to improve the biosynthesis of enzymes, antifungal agents, prebiotics or different types of secondary metabolites.
Highlights
Penicillium chrysogenum as a Platform for the Biotechnology of Fungal ProductsPenicillium section chrysogena is a large group of fungi that includes 18 Penicillium species [1] with important different characteristics
By comparing in the strains P. chrysogenum Wis54-1255 and P. chrysogenum NCPC10086 the genes involved in phenylacetic acid hydroxylation, that degrade this precursor of penicillin biosynthesis, these authors found that the pahA gene is identical in both strains, including the distinct amino acid sequence reported by Rodríguez-Sáiz et al [15] that is different in the wild type P. chrysogenum NRRL1951 with respect to the P. notatum Fleming strain
The recent availability of the genomes of P. chrysogenum KF-25 isolated from a soil sample in China and P. chrysogenum HKF2 isolated from a sludge plant treatment [25,26] provide new insight into the characteristics of non-classical P. chrysogenum strains that may lead to the discovery of new compounds relevant in: (1) human health, such as prebiotics; (2) in agriculture and plant protection [25]; or (3) new molecules with interesting pharmacological properties, e.g., antifungal proteins [58]
Summary
Penicillium section chrysogena is a large group of fungi that includes 18 Penicillium species [1] with important different characteristics. The penicillin gene cluster of P. notatum maps in chromosome II, in contrast to what was found in P. chrysogenum These differences may be explained by divergent evolution in the last centuries in the distinct habitats from which they were isolated; the Fleming strain is considered a building indoor contaminant strain as other air-borne Penicillium species, whereas the P. chrysogenum Wis54-1255 strain derives from P. chrysogenum NRRL1951, isolated from a moldy cantaloupe [2]. Some of the most relevant enzymes include exo-inulinase and β-fructofuranosidase, which have potential for the formation of inulinin oligosaccharides and fructose oligosaccharides prebiotics Since this strain was isolated from a habitat completely different from the soil, it would be very interesting to study the genes for secondary metabolism in P. chrysogenum HKF2
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