Protozoan growth rates on secondary-metabolite-producing Pseudomonas spp. correlate with high-level protozoan taxonomy

Abstract

Different features can protect bacteria against protozoan grazing, for example large size, rapid movement, and production of secondary metabolites. Most papers dealing with these matters focus on bacteria. Here, we describe protozoan features that affect their ability to grow on secondary-metabolite-producing bacteria, and examine whether different bacterial secondary metabolites affect protozoa similarly. We investigated the growth of nine different soil protozoa on six different Pseudomonas strains, including the four secondary-metabolite-producing Pseudomonas fluorescens DR54 and CHA0, Pseudomonas chlororaphis MA342 and Pseudomonas sp. DSS73, as well as the two nonproducers P. fluorescens DSM50090(T) and P. chlororaphis ATCC43928. Secondary metabolite producers affected protozoan growth differently. In particular, bacteria with extracellular secondary metabolites seemed more inhibiting than bacteria with membrane-bound metabolites. Interestingly, protozoan response seemed to correlate with high-level protozoan taxonomy, and amoeboid taxa tolerated a broader range of Pseudomonas strains than did the non-amoeboid taxa. This stresses the importance of studying both protozoan and bacterial characteristics in order to understand bacterial defence mechanisms and potentially improve survival of bacteria introduced into the environment, for example for biocontrol purposes.

The prey’s scent – Volatile organic compound mediated interactions between soil bacteria and their protist predators

“…Opposing effects observed in VOC-mediated and direct trophic interactions support the idea that bacteria and protist predators engage in a complex chemical warfare (Mazzola et al, 2009;Jousset, 2012). Thereby, besides producing soluble toxic compounds in the presence of the predator (Mazzola et al, 2009, Pedersen et al, 2011Jousset, 2012), bacteria can repel potential predators by volatiles, which is in line with a report revealing inhibition of the protist Acanthamoeba castellanii by bacterial VOCs (Kai et al, 2009).…”

“…The bacteria tested in this study produce distinct blends of volatiles (Garbeva et al, 2014;Schulz-Bohm et al, 2015) that can explain the varying responses of the protist taxa. Species-specific bacteria − protist interactions are in line with differential feeding (Glücksman et al, 2010) and the sensitivity to soluble (toxic) bacterial secondary metabolites of protist taxa (Pedersen et al, 2011).…”

The ecological role of volatile mediated interactions belowground

“…Opposing effects observed in VOCs-mediated and direct trophic interactions support the idea that bacteria and protist predators engage in a complex chemical warfare (Mazzola et al 2009;Jousset 2012). Thereby besides producing soluble toxic compounds in presence of the predator (Mazzola et al 2009;Pedersen et al 2011;Jousset 2012), bacteria can repel potential predators by volatiles, which is in line with a report revealing inhibition of the protist Acanthamoeba castellanii by bacterial VOCs ). Figure S4.1) in three species (panels a, b and c) in volatile-mediated (red bars) and direct trophic (blue bars) interactions.…”

“…The bacteria tested in this study produce distinct blends of volatiles (Garbeva et al 2014b; that can explain the varying responses of the protist taxa. Species-specific bacterial-protist interactions are in line with differential feeding (Glücksman et al 2010) and the sensitivity to soluble (toxic) bacterial secondary metabolites of protist taxa (Pedersen et al 2011). …”

Aminobacter MSH1-Mineralisation of BAM in Sand-Filters Depends on Biological Diversity

“…After three weeks, when the CO 2 -production had levelled out, we considered the inocula to be ready. The rationale behind this procedure is that it will produce communities with very different biological diversity but similar, if not completely identical, microbial biomass [20]. …”