Two new species of Penicillium (Eurotiales, Aspergillaceae) and the first record of P. danzhouense from mangrove sediment in Thailand, with notes on antibacterial activity

Two novel species of <i>Penicillium</i>, comprising <i>P. chanthaburiense</i> <b>sp. nov.</b> and <i>P. buranakarlianum</i> <b>sp. nov.</b>, were isolated from mangrove sediment collected at the King Rama IX International Mangrove Botanical Garden in Chanthaburi Province, Thailand. Morphological characterization combined with multilocus phylogenetic analyses of the internal transcribed spacer (ITS), β-tubulin (<i>TUB</i>), calmodulin (<i>CaM</i>), and RNA polymerase II second largest subunit (RPB2) genes placed <i>P. chanthaburiense</i> <b>sp. nov.</b> as a new member of section Exilicaulis, series <i>Erubescentia</i>, while <i>P. buranakarlianum</i> <b>sp. nov.</b> was assigned to section Lanata-Divaricata, series <i>Janthinella</i>. In addition, this study reports the first record of <i>P. danzhouense</i> from mangrove sediment in Thailand. Diagnostic morphological and molecular features distinguishing these taxa from their closest phylogenetic relatives are presented. These findings enrich the taxonomic framework of <i>Penicillium</i> and contribute to the understanding of fungal biodiversity in mangrove ecosystems. Furthermore, <i>P. chanthaburiense</i> <b>sp. nov.</b> exhibited antibacterial activity against several clinically relevant Gram-positive pathogens, including methicillin-resistant <i>Staphylococcus aureus</i> (MRSA), highlighting the potential of mangrove-derived <i>Penicillium</i> species in antimicrobial research.