Source-Sink Dynamics in a Two-Patch SI Epidemic Model with Life Stages and No Recovery from Infection.

This study presents a comprehensive analysis of a two-patch, two-life stage SI model without recovery from infection, focusing on the dynamics of disease spread and host population viability in natural populations. The model, inspired by real-world ecological crises like the decline of amphibian populations due to chytridiomycosis and sea star populations due to Sea Star Wasting Disease, aims to understand the conditions under which a sink host population can present ecological rescue from a healthier, source population. Mathematical and numerical analyses reveal the critical roles of the basic reproductive numbers of the source and sink populations, the maturation rate, and the dispersal rate of juveniles in determining population outcomes. The study identifies basic reproduction numbers R 0 for each of the patches, and conditions for the basic reproduction numbers to produce a receiving patch under which its population. These findings provide insights into managing natural populations affected by disease, with implications for conservation strategies, such as the importance of maintaining reproductively viable refuge populations and considering the effects of dispersal and maturation rates on population recovery. The research underscores the complexity of host-pathogen dynamics in spatially structured environments and highlights the need for multi-faceted approaches to biodiversity conservation in the face of emerging diseases.

Bioprospecting from cultivable bacterial communities of marine sediment and invertebrates from the underexplored Ubatuba region of Brazil.

Shrimp fisheries along the Brazilian coast have significant environmental impact due to high by-catch rates (21 kg per kilogram of shrimp). Typically discarded, by-catch contains many invertebrates that may host a great variety of bacterial genera, some of which may produce bioactive natural products with biotechnological applications. Therefore, to utilize by-catch that is usually discarded we explored the biotechnological potential of culturable bacteria of two abundant by-catch invertebrate species, the snail Olivancillaria urceus and the sea star Luidia senegalensis. Sediment from the collection area was also investigated. Utilizing multiple isolation approaches, 134 isolates were obtained from the invertebrates and sediment. Small-subunit rRNA (16S) gene sequencing revealed that the isolates belonged to Proteobacteria, Firmicutes and Actinobacteria phyla and were distributed among 28 genera. Several genera known for their capacity to produce bioactive natural products (Micromonospora, Streptomyces, Serinicoccus and Verrucosispora) were retrieved from the invertebrate samples. To query the bacterial isolates for their ability to produce bioactive metabolites, all strains were fermented and fermentation extracts profiled by UP LC-HRMS and tested for antimicrobial activity. Four strains exhibited antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus warneri.

Comparative study of in vivo and in vitro phagocytosis including germicidal capacity in Odontaster validus (Koehler, 1906) at 0 degree C.

The phagocytosis and germicidal capacity of Saccharomyces cerevisiae by phagocytic amoebocytes (PA) of the Antarctic starfish Odontaster validus were studied in vivo (after incubation periods of 1, 2, and 4 h) and in vitro (after incubation periods of 1, 2, 4, 8, and 12 h) at 0 degree C. The total number of PA and the phagocytic capacity (PC), phagocytic index (PI), and germicidal capacity (GC) of the PA were calculated. Results showed significant variability of the total PA number in different animals. There was a significant increase in PC and no significant differences in PI and GC for different in vitro incubation times. In vivo, experiments showed no significant difference of PC and PI, but there was a significant increase in GC as incubation periods increased. Comparison between in vitro and in vivo results revealed that PI and PC were significantly higher in vitro and that GC was significantly higher in vivo. The present study shows for the first time the phagocytosis and GC of an Antarctic invertebrate in vivo at low temperature (0 degree C), and the results are comparing with the available literature for echinoderms.