Cadiolide analogues and their precursors as new inhibitors of bacterial quorum sensing and biofilm formation

Marine natural products

Covering: January to the end of December 2022This review covers the literature published in 2022 for marine natural products (MNPs), with 645 citations (633 for the period January to December 2022) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1417 in 384 papers for 2022), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of NP structure class diversity in relation to biota source and biome is discussed.

Effects of Synthetic Tetronamides and Methylated Denigrins on Bacterial Quorum Sensing and Biofilm Formation

Detrimental biofilms of bacterial pathogens cause chronic infections with a high-level tolerance to antibiotics. To identify new control agents, we synthesized and tested a total of 14 tetronamides (including 5 new compounds) and 6 denigrin intermediates on the model species Escherichia coli. At a concentration of 50 μg/mL, two tetronamides and two methylated denigrins exhibited significant inhibitory effects against biofilm formation of E. coli RP437, e.g., by 60 and 94%, respectively. Structural analysis of the tested compounds revealed that p-methoxybenzylidene and p-methoxyphenethyl moieties of denigrins are important for biofilm inhibition, while the former group is also essential to the activity against quorum sensing (QS) via AI-2. Specifically, tetramethyldenigrin B has strong inhibitory effects against both E. coli biofilm formation and AI-2-mediated QS and thus provides a promising lead structure for designing better control agents. Consistently, tetramethyldenigrin B also showed inhibitory activity against biofilm formation of uropathogenic E. coli. Together, these findings provide new insights for the rational design of novel biofilm and QS inhibitors.

The mixed biofilm formed by Listeria monocytogenes and other bacteria: Formation, interaction and control strategies

Listeria monocytogenes is an important foodborne pathogen. It can adhere to food or food contact surface for a long time and form biofilm, which will lead to equipment damage, food deterioration, and even human diseases. As the main form of bacteria to survive, the mixed biofilms often exhibit higher resistance to disinfectants and antibiotics, including the mixed biofilms formed by L. monocytogenes and other bacteria. However, the structure and interspecific interaction of the mixed biofilms are very complex. It remains to be explored what role the mixed biofilm could play in the food industry. In this review, we summarized the formation and influence factors of the mixed biofilm developed by L. monocytogenes and other bacteria, as well as the interspecific interactions and the novel control measures in recent years. Moreover, the future control strategies are prospected, in order to provide theoretical basis and reference for the research of the mixed biofilms and the targeted control measures.