Dataset Information

Phylogeographical patterns among Mediterranean sepiolid squids and their Vibrio symbionts: environment drives specificity among sympatric species.

ABSTRACT: Bobtail squid from the genera Sepiola and Rondeletiola (Cephalopoda: Sepiolidae) form mutualistic associations with luminous Gram-negative bacteria (Gammaproteobacteria: Vibrionaceae) from the genera Vibrio and Photobacterium. Symbiotic bacteria proliferate inside a bilobed light organ until they are actively expelled by the host into the surrounding environment on a diel basis. This event results in a dynamic symbiont population with the potential to establish the symbiosis with newly hatched sterile (axenic) juvenile sepiolids. In this study, we examined the genetic diversity found in populations of sympatric sepiolid squid species and their symbionts by the use of nested clade analysis with multiple gene analyses. Variation found in the distribution of different species of symbiotic bacteria suggests a strong influence of abiotic factors in the local environment, affecting bacterial distribution among sympatric populations of hosts. These abiotic factors include temperature differences incurred by a shallow thermocline, as well as a lack of strong coastal water movement accompanied by seasonal temperature changes in overlapping niches. Host populations are stable and do not appear to have a significant role in the formation of symbiont populations relative to their distribution across the Mediterranean Sea. Additionally, all squid species examined (Sepiola affinis, S. robusta, S. ligulata, S. intermedia, and Rondeletiola minor) are genetically distinct from one another regardless of location and demonstrate very little intraspecific variation within species. These findings suggest that physical boundaries and distance in relation to population size, and not host specificity, are important factors in limiting or defining gene flow within sympatric marine squids and their associated bacterial symbionts in the Mediterranean Sea.

SUBMITTER: Zamborsky DJ

PROVIDER: S-EPMC3020525 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Phylogeographical patterns among Mediterranean sepiolid squids and their Vibrio symbionts: environment drives specificity among sympatric species.

Zamborsky D J DJ Nishiguchi M K MK

Applied and environmental microbiology 20101112 2

Bobtail squid from the genera Sepiola and Rondeletiola (Cephalopoda: Sepiolidae) form mutualistic associations with luminous Gram-negative bacteria (Gammaproteobacteria: Vibrionaceae) from the genera Vibrio and Photobacterium. Symbiotic bacteria proliferate inside a bilobed light organ until they are actively expelled by the host into the surrounding environment on a diel basis. This event results in a dynamic symbiont population with the potential to establish the symbiosis with newly hatched s ...[more]

PMID: 21075896

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Project description:BACKGROUND:Termites of the subfamily Macrotermitinae live in a mutualistic symbiosis with basidiomycete fungi of the genus Termitomyces. Here, we explored interaction specificity in fungus-growing termites using samples from 101 colonies in South-Africa and Senegal, belonging to eight species divided over three genera. Knowledge of interaction specificity is important to test the hypothesis that inhabitants (symbionts) are taxonomically less diverse than 'exhabitants' (hosts) and to test the hypothesis that transmission mode is an important determinant for interaction specificity. RESULTS:Analysis of Molecular Variance among symbiont ITS sequences across termite hosts at three hierarchical levels showed that 47 % of the variation occurred between genera, 18 % between species, and the remaining 35 % between colonies within species. Different patterns of specificity were evident. High mutual specificity was found for the single Macrotermes species studied, as M. natalensis was associated with a single unique fungal haplotype. The three species of the genus Odontotermes showed low symbiont specificity: they were all associated with a genetically diverse set of fungal symbionts, but their fungal symbionts showed some host specificity, as none of the fungal haplotypes were shared between the studied Odontotermes species. Finally, bilaterally low specificity was found for the four tentatively recognized species of the genus Microtermes, which shared and apparently freely exchanged a common pool of divergent fungal symbionts. CONCLUSION:Interaction specificity was high at the genus level and generally much lower at the species level. A comparison of the observed diversity among fungal symbionts with the diversity among termite hosts, indicated that the fungal symbiont does not follow the general pattern of an endosymbiont, as we found either similar diversity at both sides or higher diversity in the symbiont. Our results further challenge the hypothesis that transmission-mode is a general key-determinant of interaction specificity in fungus-growing termites.

Project description:Symbioses between bacteria and their insect hosts can range from loose associations through to obligate interdependence. While fundamental evolutionary insights have been gained from the in-depth study of obligate mutualisms, there is increasing interest in the evolutionary potential of flexible symbiotic associations between hosts and their gut microbiomes. Understanding relationships between microbes and hosts also offers the potential for exploitation for insect control. Here, we investigate the gut microbiome of a global agricultural pest, the Mediterranean fruit fly (Ceratitis capitata). We used 16S rRNA profiling to compare the gut microbiomes of laboratory and wild strains raised on different diets and from flies collected from various natural plant hosts. The results showed that medfly guts harbour a simple microbiome that is primarily determined by the larval diet. However, regardless of the laboratory diet or natural plant host on which flies were raised, Klebsiella spp. dominated medfly microbiomes and were resistant to removal by antibiotic treatment. We sequenced the genome of the dominant putative Klebsiella spp. ('Medkleb') isolated from the gut of the Toliman wild-type strain. Genome-wide ANI analysis placed Medkleb within the K. oxytoca / michiganensis group. Species level taxonomy for Medkleb was resolved using a mutli-locus phylogenetic approach - and molecular, sequence and phenotypic analyses all supported its identity as K. michiganensis. Medkleb has a genome size (5825435 bp) which is 1.6 standard deviations smaller than the mean genome size of free-living Klebsiella spp. Medkleb also lacks some genes involved in environmental sensing. Moreover, the Medkleb genome contains at least two recently acquired unique genomic islands as well as genes that encode pectinolytic enzymes capable of degrading plant cell walls. This may be advantageous given that the medfly diet includes unripe fruits containing high proportions of pectin. The results suggest that the medfly harbours a commensal gut bacterium that may have developed a mutualistic association with its host and provide nutritional benefits.

Dataset Information

Phylogeographical patterns among Mediterranean sepiolid squids and their Vibrio symbionts: environment drives specificity among sympatric species.

Publications

Phylogeographical patterns among Mediterranean sepiolid squids and their Vibrio symbionts: environment drives specificity among sympatric species.

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