Biology subjects

Rozen, D.

Publications and source records attributed to Rozen, D..

4 recordsLinked to original sources

bioRxiv2017

Fitness effects and transmission of phoretic nematodes of the burying beetle, Nicrophorus vespilloides

O_LINicrophorus vespilloides is a cosmopolitan social beetle that rears its offspring on decomposing carrion. Wild beetles are frequently associated with two types of macrobial symbionts, mites and nematodes.\nC_LIO_LIAlthough these organisms are believed to be phoretic commensals that harmlessly use beetles as a means of transfer between carcasses, the role of these symbionts on N. vespilloides fitness is poorly understood. Here we show that nematodes have significant negative effects on beetle fitness across a range of worm densities and also quantify the density-dependent transmission of worms between mating individuals and from parents to offspring.\nC_LIO_LIUsing field-caught beetles, we provide the first report of a new nematode symbiont in N. vespilloides, most closely related to Rhabditoides regina, and show that worm densities are highly variable across individuals isolated from nature but do not differ between males and females. Next, by inoculating mating females with increasing densities of nematodes, we show that worm infections significantly reduce brood size, larval survival and larval mass, and also eliminate the trade-off between brood size and larval mass. Finally, we show that nematodes are efficiently transmitted between mating individuals and from mothers to larvae, directly and indirectly via the carcass, and that worms persist through pupation.\nC_LIO_LIThese results show that the phoretic nematode R. regina can be highly parasitic to burying beetles but can nevertheless persist because of efficient mechanisms of intersexual and intergenerational transmission.\nC_LIO_LIPhoretic species are exceptionally common and may cause significant harm to their hosts, even though they rely on these larger species for transmission to new resources. However, this harm may be inevitable and unavoidable if transmission of phoretic symbionts requires nematode proliferation. It will be important to determine the generality of our result for other phoretic associates of animals.\nC_LI

ecology↗

bioRxiv2017

Gut microbiota in the burying beetle, Nicrophorus vespilloides, provide colonization resistance against larval bacterial pathogens

Carrion beetles, Nicrophorus vespilloides, are reared on decomposing vertebrate carrion where larvae are exposed to high-density populations of carcass-derived bacteria. We previously showed that larvae do not become colonized with these bacteria, but instead are colonized with the gut microbiome of their parents. These results suggested that bacteria in the beetle microbiome outcompete the carcass derived species for colonization of the larval gut. Here we test this hypothesis directly and quantify the fitness consequences of colonization of the Nicrophorus larval gut with different bacterial symbionts, including the insect pathogen Serratia marcescens. First, we show that beetles colonized by their endogenous microbiome produce significantly heavier broods than those colonized with carcass-bacteria. Next, we show that bacteria from the endogenous microbiome, including Providencia rettgeri and Morganella morganii, are better colonizers of the beetle gut and can outcompete non-endogenous species, including S. marcescens and Escherichia coli, during in vivo competition. Finally, we find that Providencia and Morganella provide beetles with colonization resistance against Serratia and thereby reduce Serratia-induced larval mortality during co-inoculation. Importantly, this effect is eliminated in larvae first colonized by Serratia, suggesting that while competition within the larval gut is strongly determined by priority effects, these effects are less important for Serratia-induced mortality. Our work supports the idea that bacterial gut symbionts provide direct benefits to Nicrophorus larvae by outcompeting potential bacterial pathogens. They further suggest that one benefit of parental care in Nicrophorus vespilloides is the social transmission of the microbiome from caring parents to their offspring.

microbiology↗

bioRxiv2016

Colonization and transmission of the gut microbiotaof the burying beetle, Nicrophorus vespolloides,through development

Carrion beetles in the genus Nicrophorus rear their offspring on decomposing carcasses where larvae are exposed to a diverse microbiome of decomposer bacteria. Parents coat the carcass with antimicrobial secretions prior to egg hatch (defined as Pre-Hatch care) and also feed regurgitated food, and potentially bacteria, to larvae throughout development (defined as Full care). Here we partition the roles of pre- and post-hatch parental care in the transmission and persistence of culturable symbiotic bacteria to larvae. Using three treatment groups (Full-Care, Pre-Hatch care only, and No Care), we found that larvae receiving Full-Care are predominantly colonized by bacteria resident in the maternal gut, while larvae receiving No Care are colonized exclusively with bacteria from the carcass. More importantly, larvae receiving only Pre-Hatch care were also predominantly colonized by maternal bacteria; this result indicates that parental treatment of the carcass, including application of bacteria to the carcass surface, is sufficient to ensure symbiont transfer even in the absence of direct larval feeding. Later in development, we found striking evidence that pupae undergo a aposymbiotic stage, after which they are recolonized at eclosion with bacteria shed in the moulted larval cuticle and on the wall of the pupal chamber. Our results clarify the importance of pre-hatch parental care for symbiont transmission in Nicrophorus vespilloides, and suggest that these bacteria successfully outcompete decomposer bacteria during larval and pupal gut colonization.\n\nImportanceHere we examine the origin and persistence of the culturable gut microbiota of larvae in the burying beetle Nicrophorus vespilloides. This insect is particularly interesting for this study because larvae are reared on decomposing vertebrate carcasses where they are exposed to high-densities of carrion-decomposing microbes. Larvae also receive extensive parental care in the form of carcass preservation and direct larval feeding. We find that parents transmit their gut bacteria to larvae both directly, through regurgitation, and indirectly via their effects on the carcass. In addition, we find that larvae become aposymbiotic during pupation, but are recolonized from bacteria shed onto the insect cuticle before adult eclosion. Our results highlight the diverse interactions between insect behavior and development on microbiota composition. They further indicate that strong competitive interactions mediate the bacterial composition of Nicrophorus larvae, suggesting that the bacterial communities of these insects may be highly coevolved with their host species.

ecology↗

bioRxiv2016

Crosstalk and eavesdropping among quorum sensing peptide signals that regulate bacteriocin production in Streptococcus pneumoniae

Quorum sensing (QS), where bacteria secrete and respond to chemical signals to coordinate population-wide behaviors, has revealed that bacteria are highly social. Here, we investigate how diversity in QS signals and receptors can modify social interactions controlled by the QS system regulating bacteriocin secretion in Streptococcus pneumoniae, encoded by the blp operon (bacteriocin-like peptide). Analysis of 4 096 pneumococcal genomes detected nine blp QS signals (BlpC) and five QS receptor groups (BlpH). Imperfect concordance between signals and receptors suggested widespread social interactions between cells, specifically eavesdropping (where cells respond to signals that they do not produce) and crosstalk (where cells produce signals that non-clones detect). This was confirmed in vitro by measuring the response of reporter strains containing each of six different blp QS receptors to cognate and non-cognate peptides. Assays between pneumococcal colonies grown adjacent to one another provided further evidence that crosstalk and eavesdropping occur at endogenous levels of signal secretion. Finally, simulations of QS strains producing bacteriocins revealed that eavesdropping can be evolutionarily beneficial even when the affinity for non-cognate signals is very weak. Our results highlight that social interactions can mediate intraspecific competition among bacteria and reveal that competitive interactions can be modified by polymorphic QS systems.

microbiology↗