Sterile Surfaces of <i>Mnemiopsis leidyi</i> (Ctenophora) in Bacterial Suspension—A Key to Invasion Success?

Abstract

Seawater is a dense microbial suspension with >10 6 prokaryotic and >10 4 eukaryotic propagules per milliliter. Hence, submerged surfaces get immediately covered by biofilm-forming colonizers upon contact with seawater. Since biofilms may reduce individual fitness through decreasing motility and attractiveness or increasing shearing stress by water currents and infection risk by pathogens, marine organisms have evolved countermeasures to regulate the number of surface-colonizers; alternatively they tolerate settlement and biofilm-formation. Antimicrobial defense mechanisms co-evolved with potentially colonizing microbes. By contrast, non-native animals (neozoa) are confronted with novel microbial colonizers upon colonizing a new habitat, and are expected to be less well protected against surface-colonization. Here we present results of a thorough screening of the epithelial surface of the ctenophore Mnemiopsis leidyi, being non-native in European marine environments, for epithelial bacteria and archaea. Neither light-and electronmicroscopic inspection nor PCR-screening for bacterial and archaeal DNA of 134 adult specimens from different collection sites in the Western Baltic revealed any presence of prokaryotes on the surface epithelium of comb jellies in a recently invaded environment. A limited number of bacterial associates became evident from whole-body extracts of both juvenile and adult comb jellies. Their taxonomic diversity, however, was significantly lower in adult than in juvenile specimens, suggesting a maturation of anti-microbial defense upon ontogenetic development. The mechanisms underlying the effective defense of Mnemiopsis against microbial colonization, however, remain unknown. Based on our findings, we propose 1) to make use of invasion events as natural space-for-time experiments on how symbiotic interactions change upon environmental change; and 2) to study basal metazoan animals, such as ctenophores, to understand the evolutionary ba-* Corresponding author. S. Hammann et al. 238sics of symbiont-host interactions.

Microbiota Differences of the Comb Jelly Mnemiopsis leidyi in Native and Invasive Sub-Populations

“…We demonstrated that the microbiota was significantly different from the surrounding seawater and specific to each analyzed sub-population. Contrary to the previous report of Hammann et al (2015) describing that the outer surface of M. leidyi is free from associated microbes (Hammann et al, 2015), we observed a highly diverse microbiota on epithelial tissues. Additionally, and in line with Dinasquet et al (2012), we detected different community patterns on the outer surface of the animals compared to the gastric cavity.…”

“…Some earlier studies already characterized the associated microbiome of M. leidyi in invaded (Hao et al, 2015) and native (Daniels and Breitbart, 2012) sub-populations, but came to inconclusive results. Moreover, the study by Hammann et al (2015) even claimed that M. leidyi epithelia in invaded habitats do not contain an associated microbiome (Hammann et al, 2015), which was, however, not confirmed by others (Dinasquet et al, 2012). Thus, the objectives of this study are to investigate (1) the effect of M. leidyi sub-population origin on the microbiota diversity, (2) the bacterial community differentiation between specific M. leidyi tissue compartments and 3) assess differences in the microbiome of native versus invasive sub-populations by using standardized sampling and sequencing methods.…”

Microbiota differences of the comb jelly Mnemiopsis leidyi in native and invasive sub-populations

“…The microbiome was specific to each sub-population and significantly different from the respective surrounding water. Contrary to the previous report that the mucus and epidermis of M. leidyi is free from associated microbes (Hammann et al, 2015), we observed a diverse and distinctly different microbial community composition on epithelia tissue as well as the gastrodermis, in line with Dinasquet et al (2012).…”

“…Some earlier studies characterized the associated microbiome of M. leidyi in invaded (Hao et al, 2015) and native (Daniels et al, 2012) populations but came to inconclusive results. For example, the study by Hamman et al (2015) claimed that M. leidyi epithelia in invaded habitats do not contain an associated microbiome (Hammann et al, 2015), which was, however, not confirmed by others (Dinasquet et al, 2012). The aim of the current study was to characterize the microbiome of the ctenophore Mnemiopsis leidyi in relation to the host genotype and considering different host tissues using standardized sampling and sequencing methods.…”

Discovery, Prevalence, and Persistence of Novel Circular Single-Stranded DNA Viruses in the Ctenophores Mnemiopsis leidyi and Beroe ovata

“…Ctenophores have been shown to have a variety of invertebrate parasites and symbionts (Ohtsuka et al, 2009 ), including parasitic anemones (Bumann and Puls, 1996 ; Reitzel et al, 2007 ), platyhelminth worms (Yip, 1984 ; Martorelli, 2001 ), hyperiid amphipods (Sorarrain et al, 2001 ; Gasca and Haddock, 2004 ), peritrich ciliates (Duggins et al, 1989 ; Estes et al, 1997 ), rhizopod amoebae (Moss et al, 2001a ), and dinoflagellates (Mills and McLean, 1991 ). The presence of bacteria in ctenophores was initially noted through microscopy (Moss et al, 2001b ) and culture-based methods (Saeedi et al, 2013 ); however, a number of recent studies examining ctenophore-bacterial interactions have also indicated that ctenophores maintain unique bacterial assemblages that are distinct from the surrounding water (Moss et al, 2001b ; Daniels and Breitbart, 2012 ; Dinasquet et al, 2012a ; Hammann et al, 2015 ; Hao et al, 2015 ).…”