scholarly journals The dilution effect limits plasmid horizontal transmission in multispecies bacterial communities

Microbiology ◽  
2021 ◽  
Vol 167 (9) ◽  
Author(s):  
Anastasia Kottara ◽  
Laura Carrilero ◽  
Ellie Harrison ◽  
James P. J. Hall ◽  
Michael A. Brockhurst
Keyword(s):  
Host Species ◽  
Bacterial Communities ◽  
Horizontal Transmission ◽  
Dilution Effect ◽  
Infection Risk ◽  
Host Cells ◽  
Evolutionary Innovation ◽  
Genomic Divergence ◽  
Plasmid Diversity ◽  
Plasmid Conjugation

By transferring ecologically important traits between species, plasmids drive genomic divergence and evolutionary innovation in their bacterial hosts. Bacterial communities are often diverse and contain multiple coexisting plasmids, but the dynamics of plasmids in multi-species communities are poorly understood. Here, we show, using experimental multi-species communities containing two plasmids, that bacterial diversity limits the horizontal transmission of plasmids due to the ‘dilution effect’; this is an epidemiological phenomenon whereby living alongside less proficient host species reduces the expected infection risk for a focal host species. In addition, plasmid horizontal transmission was also affected by plasmid diversity, such that the rate of plasmid conjugation was reduced from co-infected host cells carrying both plasmids. In diverse microbial communities, plasmid spread may be limited by the dilution effect and plasmid–plasmid interactions, reducing the rate of horizontal transmission.

scholarly journals The dilution effect limits plasmid horizontal transmission in multispecies bacterial communities

2021 ◽  
Author(s):  
Anastasia Kottara ◽  
Laura Carrilero ◽  
Ellie Harrison ◽  
James Peter John Hall ◽  
Michael Brockhurst
Keyword(s):  
Host Species ◽  
Bacterial Communities ◽  
Horizontal Transmission ◽  
Dilution Effect ◽  
Infection Risk ◽  
Host Cells ◽  
Evolutionary Innovation ◽  
Genomic Divergence ◽  
Plasmid Diversity ◽  
Plasmid Conjugation

By transferring ecologically important traits between species, plasmids drive genomic divergence and evolutionary innovation in their bacterial hosts. Bacterial communities are often diverse and contain multiple coexisting plasmids, but the dynamics of plasmids in multispecies communities are poorly understood. Here, we show, using experimental multispecies communities containing two plasmids, that bacterial diversity limits the horizontal transmission of plasmids due to the dilution effect; an epidemiological phenomenon whereby living alongside less proficient host species reduces the expected infection risk for a focal host species. In addition, plasmid horizontal transmission was also affected by plasmid diversity, such that the rate of plasmid conjugation was reduced from coinfected host cells carrying both plasmids. In diverse microbial communities, plasmid spread may be limited by the dilution effect and plasmid-plasmid interactions reducing the rate of horizontal transmission.

scholarly journals Why do plasmids manipulate the expression of bacterial phenotypes?

2021 ◽  
Vol 377 (1842) ◽  
Author(s):  
Kathryn Billane ◽  
Ellie Harrison ◽  
Duncan Cameron ◽  
Michael A. Brockhurst
Keyword(s):  
Side Effects ◽  
Host Cell ◽  
Vertical Transmission ◽  
Horizontal Transmission ◽  
Host Cells ◽  
Gene Exchange ◽  
Theme Issue ◽  
Adaptive Traits ◽  
Evolutionary Role ◽  
Plasmid Conjugation

Conjugative plasmids play an important role in bacterial evolution by transferring niche-adaptive traits between lineages, thus driving adaptation and genome diversification. It is increasingly clear, however, that in addition to this evolutionary role, plasmids also manipulate the expression of a broad range of bacterial phenotypes. In this review, we argue that the effects that plasmids have on the expression of bacterial phenotypes may often represent plasmid adaptations, rather than mere deleterious side effects. We begin by summarizing findings from untargeted omics analyses, which give a picture of the global effects of plasmid acquisition on host cells. Thereafter, because many plasmids are capable of both vertical and horizontal transmission, we distinguish plasmid-mediated phenotypic effects into two main classes based upon their potential fitness benefit to plasmids: (i) those that promote the competitiveness of the host cell in a given niche and thereby increase plasmid vertical transmission, and (ii) those that promote plasmid conjugation and thereby increase plasmid horizontal transmission. Far from being mere vehicles for gene exchange, we propose that plasmids often act as sophisticated genetic parasites capable of manipulating their bacterial hosts for their own benefit. This article is part of the theme issue ‘The secret lives of microbial mobile genetic elements’.

scholarly journals Investigating diversity, evolution, development and physiology of red algal parasites from New Zealand

2021 ◽  
Author(s):  
◽  
Maren Preuss
Keyword(s):  
Host Species ◽  
High Throughput Sequencing ◽  
Phylogenetic Analyses ◽  
Host Cells ◽  
Gene Content ◽  
Infected Host ◽  
Parasite Development ◽  
Future Research ◽  
Mitochondrial Genomes ◽  
Red Algal

<p>Red algal parasites have evolved independently over a 100 times and grow only on other red algal hosts. Most parasites are closely related to their host based on the similarity of their reproductive structures. Secondary pit connections between red algal parasites and their hosts are used to transfer parasite organelles and nuclei into host cells. Morphological and physiological changes in infected host cells have been observed in some species. Parasite mitochondrial genomes are similar in size and gene content to free-living red algae whereas parasite plastids are highly reduced. Overall, red algal parasites are poorly studied and thus the aim of this study was to increase the general knowledge of parasitic taxa with respect to their diversity, evolutionary origin, development, physiology, and organelle evolution. Investigation of the primary literature showed that most species descriptions of red algal parasites were poor and did not meet the criteria for defining a parasitic relationship. This literature study also revealed a lack of knowledge of many key parasitic processes including early parasite development, host cell “control”, and parasite origin. Many of these poorly studied research areas were addressed in this thesis. Phylogenetic analyses, using a range of markers from all three genomes (cpDNA: rbcL, nDNA: actin, LSU rRNA; mtDNA: cox1), showed different patterns of phylogenetic relationships for the four new red algal parasites and their hosts. The parasites Phycodrys novae-zelandiophila sp. nov. and Vertebrata aterrimophila sp. nov. closest relative is its host species. Cladhymenia oblongifoliophila sp. nov. closest relative is its host species based on nuclear and mitochondrial markers whereas the plastid markers group the parasite with Cladhymenia lyallii, suggesting that the parasite plastid was acquired when previously parasitizing C. lyallii. Judithia parasitica sp. nov. grows on two Blastophyllis species but the parasites’ closest relative is the non-host species Judithia delicatissima. Developmental studies of the parasite Vertebrata aterrimophila, showed a unique developmental structure (“trunk-like” cell) not known in other parasites, plus localised infection vi and few changes in infected host cells. High-throughput-sequencing revealed mitochondrial genomes of similar size, gene content and order in the parasite Pterocladiophila hemisphaerica to its host Pterocladia lucida, and a reduced non-photosynthetic plastid in the parasite. Mitochondrial (mt) and plastid (cp) genome phylogenies placed Pterocladiophila hemisphaerica on long branches, either as sister to Ceramiales (mt) or Gracilariales (cp). Further analyses, filtering non-elevated plastid genes grouped the parasite neither with the Gracilariales (mt) or Gelidiales (cp) on shorter branches but without support. Nuclear phylogeny grouped P. hemisphaerica as sister to the Gelidiales and other red algal orders and was the only phylogenetic relationship with support. Investigations of photosystem II capacity using PAM fluorometry, and quantifying chlorophyll a content in three pigmented parasites, showed different host nutrient dependencies. Rhodophyllis parasitica and Vertebrata aterrimophila are not able to photosynthesize and are fully dependent on host nutrients. Pterocladiophila hemisphaerica is able to photosynthesize independently, even though it has a reduced non-photosynthetic plastid genome, and therefore is only partially dependent on its host. This study advances our current understanding of red algal parasites and highlights many possibilities for future research including genome evolution and understanding parasite diversity.</p>

scholarly journals Blood thicker than water: kinship, disease prevalence and group size drive divergent patterns of infection risk in a social mammal

2016 ◽  
Vol 283 (1835) ◽  
pp. 20160798 ◽  
Author(s):  
Clare H. Benton ◽  
Richard J. Delahay ◽  
Andrew Robertson ◽  
Robbie A. McDonald ◽  
Alastair J. Wilson ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Molecular Genetic ◽  
Social Groups ◽  
Herd Immunity ◽  
Dilution Effect ◽  
Meles Meles ◽  
Infection Risk ◽  
Susceptibility To Infection ◽  
Molecular Genetic Data ◽  
Herd Immunity Effect

The importance of social- and kin-structuring of populations for the transmission of wildlife disease is widely assumed but poorly described. Social structure can help dilute risks of transmission for group members, and is relatively easy to measure, but kin-association represents a further level of population sub-structure that is harder to measure, particularly when association behaviours happen underground. Here, using epidemiological and molecular genetic data from a wild, high-density population of the European badger ( Meles meles ), we quantify the risks of infection with Mycobacterium bovis (the causative agent of tuberculosis) in cubs. The risk declines with increasing size of its social group, but this net dilution effect conceals divergent patterns of infection risk. Cubs only enjoy reduced risk when social groups have a higher proportion of test-negative individuals. Cubs suffer higher infection risk in social groups containing resident infectious adults, and these risks are exaggerated when cubs and infectious adults are closely related. We further identify key differences in infection risk associated with resident infectious males and females. We link our results to parent–offspring interactions and other kin-biased association, but also consider the possibility that susceptibility to infection is heritable. These patterns of infection risk help to explain the observation of a herd immunity effect in badgers following low-intensity vaccination campaigns. They also reveal kinship and kin-association to be important, and often hidden, drivers of disease transmission in social mammals.

The influence of landscape and environmental factors on ranavirus epidemiology in amphibian assemblages

2017 ◽  
Author(s):  
Brian J. Tornabene ◽  
Andrew R. Blaustein ◽  
Cheryl J. Briggs ◽  
Dana M. Calhoun ◽  
Pieter T. J. Johnson ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Host Species ◽  
Dilution Effect ◽  
Variance Partitioning ◽  
Lower Probability ◽  
Infection Prevalence ◽  
Taxonomic Richness ◽  
Amphibian Disease ◽  
Competing Models ◽  
Reservoir Hosts

ABSTRACTAimTo quantify the influence of a suite of landscape, abiotic, biotic, and host-level variables on ranavirus disease dynamics in amphibian assemblages at two biological levels (site and host-level).LocationWetlands within the East Bay region of California, USA.MethodsWe used competing models, multimodel inference, and variance partitioning to examine the influence of 16 landscape and environmental factors on patterns in site-level ranavirus presence and host-level ranavirus infection in 76 wetlands and 1,377 amphibian hosts representing five species.ResultsThe landscape factor explained more variation than any other factors in site-level ranavirus presence, but biotic and host-level factors explained more variation in host-level ranavirus infection. At both the site- and host-level, the probability of ranavirus presence correlated negatively with distance to nearest ranavirus-positive wetland. At the site-level, ranavirus presence was associated positively with taxonomic richness. However, infection prevalence within the amphibian population correlated negatively with vertebrate richness. Finally, amphibian host species differed in their likelihood of ranavirus infection: American Bullfrogs had the weakest association with infection while Western Toads had the strongest. After accounting for host species effects, hosts with greater snout-vent length had a lower probability of infection.Main conclusionsStrong spatial influences at both biological levels suggest that mobile taxa (e.g., adult amphibians, birds, reptiles) may facilitate the movement of ranavirus among hosts and across the landscape. Higher taxonomic richness at sites may provide more opportunities for colonization or the presence of reservoir hosts that may influence ranavirus presence. Higher host richness correlating with higher ranavirus infection is suggestive of a dilution effect that has been observed for other amphibian disease systems and warrants further investigation. Our study demonstrates that an array of landscape, environmental, and host-level factors were associated with ranavirus epidemiology and illustrates that their importance vary with biological level.

scholarly journals Host species, pathogens and disease associated with divergent nasal microbial communities in tortoises

2018 ◽  
Vol 5 (10) ◽  
pp. 181068
Author(s):  
Chava L. Weitzman ◽  
Franziska C. Sandmeier ◽  
C. Richard Tracy
Keyword(s):  
Host Species ◽  
Bacterial Communities ◽  
Sonoran Desert ◽  
Bacterial Community Composition ◽  
Operational Taxonomic Unit ◽  
Nasal Discharge ◽  
Microbiome Composition ◽  
Technological Advances ◽  
Repeated Sampling ◽  
Pathogen Colonization

Diverse bacterial communities are found on every surface of macro-organisms, and they play important roles in maintaining normal physiological functions in their hosts. While the study of microbiomes has expanded with the influx of data enabled by recent technological advances, microbiome research in reptiles lags behind other organisms. We sequenced the nasal microbiomes in a sample of four North American tortoise species, and we found differing community compositions among tortoise species and sampling sites, with higher richness and diversity in Texas and Sonoran desert tortoises. Using these data, we investigated the prevalence and operational taxonomic unit (OTU) diversity of the potential pathogen Pasteurella testudinis and found it to be common, abundant and highly diverse. However, the presence of this bacterium was not associated with differences in bacterial community composition within host species. We also found that the presence of nasal discharge from tortoises at the time of sampling was associated with a decline in diversity and a change in microbiome composition, which we posit is due to the harsh epithelial environment associated with immune responses. Repeated sampling across seasons, and at different points of pathogen colonization, should contribute to our understanding of the causes and consequences of different bacterial communities in these long-lived hosts.

Disruption of a host-parasite system following the introduction of an exotic host species

Parasitology ◽  
2005 ◽  
Vol 130 (6) ◽  
pp. 661-668 ◽  
Author(s):  
S. TELFER ◽  
K. J. BOWN ◽  
R. SEKULES ◽  
M. BEGON ◽  
T. HAYDEN ◽  
...  
Keyword(s):  
Bank Vole ◽  
Host Species ◽  
Negative Relationship ◽  
Dilution Effect ◽  
Wood Mouse ◽  
Clethrionomys Glareolus ◽  
Infection Prevalence ◽  
Wood Mice ◽  
Effect Hypothesis ◽  
Host Parasite

The potential of biological invasions to threaten native ecosystems is well recognized. Here we describe how an introduced species impacts on native host-parasite dynamics by acting as an alternative host. By sampling sites across an invasion front in Ireland, we quantified the influence of the introduced bank vole (Clethrionomys glareolus) on the epidemiology of infections caused by flea-transmitted haemoparasites of the genusBartonellain native wood mice (Apodemus sylvaticus).Bartonellainfections were detected on either side of the front but occurred exclusively in wood mice, despite being highly prevalent in both rodent species elsewhere in Europe. Bank vole introduction has, however, affected the wood mouse-Bartonellainteraction, with the infection prevalence of bothBartonella birtlesiiandBartonella tayloriideclining significantly with increasing bank vole density. Whilst flea prevalence in wood mice increases with wood mouse density in areas without bank voles, no such relationship is detected in invaded areas. The results are consistent with the dilution effect hypothesis. This predicts that for vector-transmitted parasites, the presence of less competent host species may reduce infection prevalence in the principal host. In addition we found a negative relationship betweenB. birtlesiiandB. tayloriiprevalences, indicating that these two microparasites may compete within hosts.

scholarly journals Tree phyllosphere bacterial communities: exploring the magnitude of intra- and inter-individual variation among host species

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2367 ◽  
Author(s):  
Isabelle Laforest-Lapointe ◽  
Christian Messier ◽  
Steven W. Kembel
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Individual Variation ◽  
Host Species ◽  
Bacterial Communities ◽  
Bacterial Community Structure ◽  
Temperate Forest ◽  
Abies Balsamea ◽  
Tree Canopy ◽  
Individual Tree

BackgroundThe diversity and composition of the microbial community of tree leaves (the phyllosphere) varies among trees and host species and along spatial, temporal, and environmental gradients. Phyllosphere community variation within the canopy of an individual tree exists but the importance of this variation relative to among-tree and among-species variation is poorly understood. Sampling techniques employed for phyllosphere studies include picking leaves from one canopy location to mixing randomly selected leaves from throughout the canopy. In this context, our goal was to characterize the relative importance of intra-individual variation in phyllosphere communities across multiple species, and compare this variation to inter-individual and interspecific variation of phyllosphere epiphytic bacterial communities in a natural temperate forest in Quebec, Canada.MethodsWe targeted five dominant temperate forest tree species including angiosperms and gymnosperms:Acer saccharum,Acer rubrum,Betula papyrifera,Abies balsameaandPicea glauca. For one randomly selected tree of each species, we sampled microbial communities at six distinct canopy locations: bottom-canopy (1–2 m height), the four cardinal points of mid-canopy (2–4 m height), and the top-canopy (4–6 m height). We also collected bottom-canopy leaves from five additional trees from each species.ResultsBased on an analysis of bacterial community structure measured via Illumina sequencing of the bacterial 16S gene, we demonstrate that 65% of the intra-individual variation in leaf bacterial community structure could be attributed to the effect of inter-individual and inter-specific differences while the effect of canopy location was not significant. In comparison, host species identity explains 47% of inter-individual and inter-specific variation in leaf bacterial community structure followed by individual identity (32%) and canopy location (6%).DiscussionOur results suggest that individual samples from consistent positions within the tree canopy from multiple individuals per species can be used to accurately quantify variation in phyllosphere bacterial community structure. However, the considerable amount of intra-individual variation within a tree canopy ask for a better understanding of how changes in leaf characteristics and local abiotic conditions drive spatial variation in the phyllosphere microbiome.

scholarly journals The Importance of Environmentally Acquired Bacterial Symbionts for the Squash Bug (Anasa tristis), a Significant Agricultural Pest

2021 ◽  
Vol 12 ◽  
Author(s):  
Tarik S. Acevedo ◽  
Gregory P. Fricker ◽  
Justine R. Garcia ◽  
Tiffanie Alcaide ◽  
Aileen Berasategui ◽  
...  
Keyword(s):  
Bacterial Communities ◽  
Horizontal Transmission ◽  
Bacterial Symbionts ◽  
Complete Understanding ◽  
Anasa Tristis ◽  
Squash Bug ◽  
The Family ◽  
Insect Symbionts ◽  
Midgut Crypts ◽  
Bacterial Plant Pathogen

Most insects maintain associations with microbes that shape their ecology and evolution. Such symbioses have important applied implications when the associated insects are pests or vectors of disease. The squash bug, Anasa tristis (Coreoidea: Coreidae), is a significant pest of human agriculture in its own right and also causes damage to crops due to its capacity to transmit a bacterial plant pathogen. Here, we demonstrate that complete understanding of these insects requires consideration of their association with bacterial symbionts in the family Burkholderiaceae. Isolation and sequencing of bacteria housed in the insects’ midgut crypts indicates that these bacteria are consistent and dominant members of the crypt-associated bacterial communities. These symbionts are closely related to Caballeronia spp. associated with other true bugs in the superfamilies Lygaeoidea and Coreoidea. Fitness assays with representative Burkholderiaceae strains indicate that the association can significantly increase survival and decrease development time, though strains do vary in the benefits that they confer to their hosts, with Caballeronia spp. providing the greatest benefit. Experiments designed to assess transmission mode indicate that, unlike many other beneficial insect symbionts, the bacteria are not acquired from parents before or after hatching but are instead acquired from the environment after molting to a later developmental stage. The bacteria do, however, have the capacity to escape adults to be transmitted to later generations, leaving the possibility for a combination of indirect vertical and horizontal transmission.

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