Effects of nutrients, salinity, pH and light:dark cycle on the production of reactive oxygen species in the alga Chattonella marina

Abstract

Experiments were carried out to investigate the effects of nutrients, salinity, pH and light:dark cycle on growth rate and production of reactive oxygen species (ROS) by Chattonella marina, a harmful algal bloom (HAB) species that often causes fish kills. Different nitrogen forms (organic-N and inorganic-N), N:P ratios, light:dark cycles and salinity significantly influenced algal growth, but not ROS production.However, iron concentration and pH significantly affected both growth and ROS production in C. marina. KCN (an inhibitor of mitochondrial respiration) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (an inhibitor of photosynthesis) had no significant effects on ROS production. Vitamin K 3 (a plasma membrane electron shuttle) enhanced ROS production while its antagonist, dicumarol, decreased ROS production. Taken together, our results suggest that ROS production by C. marina is related to a plasma membrane enzyme system regulated by iron availability but is independent of growth, photosynthesis, availability of macronutrients, salinity and irradiance.

Stable-isotope probing and metagenomics reveal predation by protozoa drives E. coli removal in slow sand filters

“…Although various studies have shown the individual importance of viral lysis, protozoan grazing, and endogenous and exogenous ROS in E. coli removal (Curtis et al, 1992;Bomo et al, 2004;Grobe et al, 2006;Liu et al, 2007;Kadir and Nelson, 2014), this is the first study, to our knowledge, to indicate the importance and interactions of all of these mechanisms for E. coli removal. Further, our approach enabled us to identify that the majority of the E. coli removal is due to top-down trophic interactions, such as protozoan grazing by M. brevicollis and T. spp and viral lysis by E. phages.…”

“…This is likely to have amplified changes in the carbonate-bicarbonate equilibrium induced by algal respiration, which has been shown to induce elevated growth rates and fruiting body formation in Sordaria spp (Elleuche and Pöggeler, 2010). This, in turn, results in further elevated CO 2 levels due to fungal respiration causing an additional imbalance in the carbonate-bicarbonate equilibrium and inducing a knock-on effect to the water pH, which has been shown to induce elevated algal ROS production (Liu et al, 2007). Such an association helps to explain the apparent mutualistic relationship displayed by fungi and algae during E. coli removal (Figure 6).…”

“…Previously, mathematical models and work in simplified microcosms have shown the individual importance of viral lysis, protozoan grazing and endogenous and exogenous ROS in E. coli removal (Curtis et al, 1992;Bomo et al 2004;Grobe et al, 2006;Liu et al, 2007;Kadir and Nelson, 2014). Within this study, the level of involvement in E. coli removal of each kingdom has been approximated from the metagenomic analysis following several assumptions.…”

“…For example, previous work has shown algae to be actively involved in E. coli removal by the production ROS (Curtis et al, 1992;Maynard et al, 1999;Feng et al, 2011), which causes lysis of E. coli and other bacterial species. In particular, extensive work has shown that Chattonella marina (one of the algae which significantly increased in labelled samples; Figure 5a) produces several ROS species (Liu et al, 2007) known to significantly reduce coliform numbers. Therefore, it is conceivable that algae are actively participating in E. coli removal by indirect mechanisms (Figure 6).…”

“…In addition, theoretical models and empirical surveys have indicated that the majority of the mortality is due to grazing by protists, and to a lesser extent to viral lysis (Pernthaler, 2005). However, abiotic factors, such as UV radiation and reactive oxygen species (ROS)-associated lysis, have also been hypothesized as potential lysis routes for microbes/pathogens (Curtis et al, 1992;Alonso-Saez et al, 2006;Liu et al, 2007;Kadir and Nelson, 2014).…”