Bacterial pathogens, virulence mechanism and host defence in marine macroalgae

Abstract

SummaryMacroalgae are important ecosystem engineers in temperate marine waters. The function of macroalgae is intimately linked to the composition and structure of their epibiotic bacterial, communities, and evidence has emerged that bacteria can also have a negative impact on their host by causing disease. A few examples exist where bacteria have been unambiguously linked to macroalgal disease, however in many cases, pathogenicity has not been clearly separated from saprophytic behaviour or secondary colonization after disease initiation. Nevertheless, pathogenic pressure by bacteria might be substantial, as macroalgae have evolved a range of innate and induced defence mechanism that have the potential to control bacterial attacks. The presence and abundance of virulence factors in marine bacteria, which have not previously been recognized as pathogens, also represents an underappreciated, opportunistic potential for disease. Given that virulence expression in opportunistic pathogens is often dependent on environmental conditions, we predict that current and future anthropogenic changes in the marine environment will lead to an increase in the occurrence of macroalgal disease. This review highlights important areas of research that require future attention to understand the link between environmental change, opportunistic pathogens and macroalgal health in the world's oceans.

Climate Change Impacts on Seagrass Meadows and Macroalgal Forests: An Integrative Perspective on Acclimation and Adaptation Potential

“…Diazotrophic heterotrophic bacteria in seagrasses rhizosphere are involved in nitrogen fixation (Welsh, 2000). Macrophyte associated bacteria are also involved in the production of biologically active and defensive compounds, protecting the host from pathogens, herbivores, fouling, and chemical intrusion (Burgess et al, 1999;Rao et al, 2007;Penesyan et al, 2009;Egan et al, 2014;Saha et al, 2014). Bacterial antimicrobial metabolites negatively affect fouling organisms and control microbial communities on macroalgae surfaces (Egan et al, 2000;Joint et al, 2007;Romero et al, 2011).…”

The cultivation of European kelp for bioenergy: Site and species selection

“…and Alteromonas spp. are known to be responsible for some disease [163], but in numerous cases, the agent has not been identified. The prevalence of endophytic infection is known to be high in wild kelp populations [164], and so there are concerns that a) pathogens may be transplanted with seaweed stocks, infecting nearby natural seaweed beds and b) as physicochemical stress is often a trigger for outbreaks in cultivated kelp [162], climate change impacts such as rising seawater temperatures may in the future lead to more severe disease impacts.…”

Novel ssDNA Viruses Detected in the Virome of Bleached, Habitat-Forming Kelp Ecklonia radiata

“…This includes stressors associated with urbanization, such as increased nutrients and sedimentation of the coastal region (Connell et al, 2008), and ocean warming, through both direct physiological effects of temperature as well as indirect effects through range extensions of herbivorous sea urchins or fishes, which consume large areas of kelp forests (Wernberg et al, 2011;Ling and Johnson, 2012;Vergés et al, 2016). Though relatively little studied in seaweed systems, microbial disease may also play a role in loss of habitat-forming seaweeds (Egan et al, 2014). Disease in marine systems appears to be increasing globally, including in communities that are dominated by primary habitat-forming organisms, such as coral reefs and kelp forests (Rosenberg et al, 2007;Vega Thurber et al, 2009;Krediet et al, 2013), and disease in seaweeds has been linked to anthropogenic stressors, such as ocean warming Case et al, 2011).…”