Countway, P. D. | bioRxiv Science

bioRxiv2021

Survival and detection of bivalve transmissible neoplasia from the soft-shell clam Mya arenaria (MarBTN) in seawater

Many pathogens can cause cancer, but cancer itself does not normally act as an infectious agent. However, transmissible cancers have been found in a few cases in nature: in Tasmanian devils, dogs, and several bivalve species. The transmissible cancers in dogs and devils are known to spread through direct physical contact, but the exact route of transmission of bivalve transmissible neoplasia (BTN) has not yet been confirmed. It has been hypothesized that cancer cells could be released by diseased animals and spread through the water column to infect/engraft into other animals. To test the feasibility of this proposed mechanism of transmission, we tested the ability of BTN cells from the soft-shell clam (Mya arenaria BTN, or MarBTN) to survive in artificial seawater. We found that BTN cells are highly sensitive to salinity, with acute toxicity at salinity levels lower than those found in their environment. BTN cells also survive longer at lower temperatures, with >48% of cells surviving a week in seawater at temperatures from 4{degrees}C to 16{degrees}C, and 49% surviving for more than two weeks at 4{degrees}C. With one clam donor, living cells were observed for more than eight weeks at 4{degrees}C. We also used qPCR of environmental DNA (eDNA) to detect the presence of BTN-specific DNA in the environment. We observed release of BTN-specific DNA into the water of aquaria from tanks with highly BTN-positive clams, and we detected BTN-specific DNA in seawater samples collected from BTN-endemic areas, although the level detected was much lower. Overall, these data show that BTN cells can survive well in seawater, and they are released into the water by diseased animals, supporting the hypothesis that BTN is spread from animal-to-animal by cells through seawater.

cancer biology↗

bioRxiv2020

Mud, microbes, and macrofauna: seasonal dynamics of the iron biogeochemical cycle in an intertidal mudflat

Microorganisms and burrowing animals exert a pronounced impact on the cycling of redox sensitive metals in coastal sediments. Sedimentary metal cycling is likely controlled by seasonal processes including changes in temperature, animal feeding behavior due to food availability, and availability of organic matter in sediments. We hypothesized that the iron biogeochemical cycle and associated sedimentary microbial community will respond to seasonal changes in a bioturbated intertidal mudflat. In this study, we monitored the spatiotemporal dynamics of porewater and highly reactive solid phase iron with the corresponding prokaryotic and eukaryotic sedimentary microbial communities over one annual cycle from November 2015 to November 2016. Continuous and seasonally variable pools of both porewater Fe(II) and highly reactive iron (FeHR) were observed throughout the season with significant increases of Fe(II) and FeHR in response to increased sediment temperature in summer months. Maximum concentrations of Fe(II) and FeHR were predominantly confined to the upper 5 cm of sediment throughout the season. Iron-oxidizing and -reducing microorganisms were present and stable throughout the season, and exhibited strong depth-dependent stratification likely due to availability of Fe(II) and FeHR pools, respectively. Otherwise, the community was dominated by Deltaproteobacteria, which are involved in sulfur and potentially iron cycling, as well as Gammaproteobacteria and Bacteroidetes. The microbial community was relatively stable throughout the seasonal cycle, but showed strong separation with depth, probably driven by changes in oxygen availability and organic matter. The relative abundance of diatoms revealed a noticeable seasonal signature, which we attribute to spring and fall blooms recorded in the sediments. Macro-, meio, and microfauna were detected throughout the season with some seasonal variations that may influence sedimentary iron transformations by active microbial grazing. The seasonal dynamics of the sedimentary iron cycle are controlled by numerous, interdependent processes, with macrobiota-microbiota relationships and depth stratification comprising primary components. Deciphering these processes in natural ecosystems is essential to understand how they might respond to future environmental perturbations, such as anthropogenic nutrient release to coastal systems.

microbiology↗