Biofilms are surface-attached multicellular communities that play critical roles in inducing biofouling and biocorrosion in the marine environment. Given the serious economic losses and problems caused by biofouling and biocorrosion, effective biofilm control strategies are highly sought after. In a screening program of antibiofilm compounds against marine biofilms, we discovered the potent biofilm inhibitory activity of elasnin. Elasnin effectively inhibited the biofilm formation of seven strains of bacteria isolated from marine biofilms. With high productivity, elasnin-based coatings were prepared in an easy and cost-effective way, which exhibited great performance in inhibiting the formation of multi-species biofilms and the attachment of large biofouling organisms in the marine environment. The 16S amplicon analysis and anti-larvae assay revealed that elasnin could prevent biofouling by the indirect impact of changed microbial composition of biofilms and direct inhibitory effect on larval settlement with low toxic effects. These findings indicated the potential application of elasnin in biofilm and biofouling control in the marine environment.

Microbes respond to environmental stimuli through complicated signal transduction systems. In microbial biofilms, because of complex multiple species interactions, signals transduction systems are of an even higher complexity. Here, we performed a signal-molecule-treatment experiment to study the role of different signal molecules, including N-hexanoyl-L-homoserine lactone (C6-HSL), N-dodecanoyl-L-homoserine lactone (C12-HSL), Pseudomonas quinolone signal (PQS), and cyclic di-GMP (c-di-GMP), in the development of marine biofilms. Comparative metagenomics suggested a distinctive influence of these molecules on the microbial structure and function of multi-species biofilm communities in its developing stage. The PQS-treated biofilms shared the least similarity with the control and initial biofilms. The role of PQS in biofilm development was further explored experimentally with the strain Erythrobacter sp. HKB8 isolated from marine biofilms. Comparative transcriptomic analysis showed that 314 genes, such as those related to signal transduction and biofilm formation, were differentially expressed in the untreated and PQS-treated Erythrobacter sp. HKB8 biofilms. Our study demonstrated the different roles of signal molecules in marine biofilm development. In particular, the PQS-based signal transduction system, which is frequently detected in marine biofilms, may play an important role in regulating microbe-microbe interactions and the assemblage of biofilm communities.

Recent discoveries indicate that tolerance and resistance could rapidly evolve in bacterial populations under intermittent antibiotic treatment. In the present study, we applied antibiotic combinations in laboratory experiments to generate novel methicillin-resistant Staphylococcus aureus strains with distinct phenotypes (tolerance, resistance, and suppressed tolerance), and compared their proteome profiles to uncover the adaptation mechanisms. While the tolerant strains have very different proteomes than the susceptible ancestral strain, the resistant strain largely resembles the ancestral in terms of their proteomes. Our proteomics data and other assays support the connection between the detected mutations to the observed phenotypes, confirming the general understanding of tolerance and resistance mechanisms. While resistance directly counteracts the action mechanism of the antibiotic, tolerance involves complex substantial changes in the cells’ biological process to achieve survival advantages. Overall, this study provides insights into the existence of diverse evolutionary pathways for tolerance and resistance development under different treatment scenarios.

Biomineralization, a key driving force underlying dramatic morphological diversity, is widely adopted by metazoans to incorporate inorganic minerals into their organic matrices. The scaly-foot snail Chrysomallon squamiferum from deep-sea hot vents uniquely possesses hundreds of sclerites on its foot in addition to a coiled shell, providing an exclusive case to study the formation of evolutionarily novel hard parts. Here, we identified the matrix proteins present in the exoskeletons of C. squamiferum and Gigantopelta aegis, a confamilial species from the same vent habitat but lacking sclerites, to uncover the genes and proteins presumably involved in the sclerite formation processes. Comparative multi-omics analyses suggest that C. squamiferum co-opted a diverse range of metazoan biocalcifying proteins through sclerite formation in a possibly deep homology scenario, and the up-regulated biomineralization-related genes in the foot imply alternative sources of sclerite proteins. The sclerite-secreting epithelium employs and utilizes genes considerably older than those in the mantle, which supports the predominant contribution of co-option in C. squamiferum sclerite formation. Our results highlight the importance of gene co-option in shaping novel hard parts in C. squamiferum and indicate that lineage-specific gene incorporation is a possible key factor leading to the rapid evolution of a novel hard structure in this vent-endemic species.

Biofilms are surface-attached multicellular communities that create many problems in human health and various industries. Given the prominence of biofilms in biofouling and infectious diseases, antibiofilm control approaches are highly sought after. In the present study, we identified elasnin as a potent antibiofilm agent through a bioassay-guided approach. Elasnin specifically inhibited the biofilm formation of bacterial mono-species and eradicated the mature biofilm of Gram-positive bacteria at concentrations below 2.5 μg/mL with a low toxic effect on cells and a low resistance risk. Confocal observations illustrated that elasnin decreased cell aggregations and destroyed the biofilm matrix. Furthermore, elasnin-based antibiofilm coatings were prepared and inhibited the formation of multi-species biofilms and the attachment of large biofouling organisms in the field test. These findings suggest that elasnin is a promising antibiofilm agent for future applications in biofilm control. Importance: Due to the increased diversity of biofilm-associated infections and the failure of conventional antimicrobial treatment, new and effective biofilm-specific pharmacologic strategies are urgently needed. Elasnin is a new antibiofilm natural product produced by Streptomyces with high efficiency and low toxicity. Elasnin effectively destroyed the biofilm matrix of Gram-positive bacteria, thus making them more susceptible to antibiotics. Unlike currently deployed antibiotic vancomycin, which exclusively targets essential life processes and kills the pathogen, elasnin did not exhibit bactericidal effect and thus held great potential in delaying resistance. With high yield, elasnin-based coatings were easily prepared with low expenditures and exhibited favorable performance in field test. Collectively, the antibiofilm properties of elasnin, combined with the low cost of supply and the low risk of resistance, could provide the basis for the development of a novel antibiofilm agent that could help fight to antibiotics resistance.