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Gammaproteobacteria as essential primary symbionts in the striped shield bug, Graphosoma Lineatum (Hemiptera: Pentatomidae)

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ABSTRACT

Many members of suborder Heteroptra harbor heritable symbiotic bacteria. Here we characterize the gut symbiotic bacterium in Graphosoma lineatum (Hemiptera: Pentatomidae) by using molecular phylogeny, real-time PCR analysis as well as light and electron microscopy observations. The microscopy observations revealed the presence of a large number of rod-shaped bacterial cells in the crypts. A very high prevalence (98 to 100%) of the symbiont infection was found in the insect populations that strongly supports an intimate association between these two organisms. Real-time PCR analysis also showed that the Gammaproteobacteria dominated the crypts. The sequences of 16sr RNA and groEL genes of symbiont showed high levels of similarity (93 to 95%) to Pantoea agglomeranse and Erwinia herbicola Gammaproteobacteria. Phylogenetic analyses placed G. lineatum symbiont in a well-defined branch, divergent from other stink bug bacterial symbionts. Co-evolutionary analysis showed lack of host-symbiont phylogenetic congruence. Surface sterilization of eggs resulted in increased pre-adult stage in the offspring (aposymbionts) in comparison to the normal. Also, fecundity, longevity, and adult stage were significantly decreased in the aposymbionts. Therefore, it seems that the symbiont might play a vital function in the host biology, in which host optimal development depends on the symbiont.

No MeSH data available.


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Light microscopy and transmission electron microscopy (TEM) of G. lineatum crypts.(a–d) Light microscopy images from enclosed crypt; a large number of bacteria as observed in the crypts. L: lumen. (e) TEM of a crypt containing symbiotic bacteria. (f) TEM of a single symbiotic bacterium in the crypt.
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f2: Light microscopy and transmission electron microscopy (TEM) of G. lineatum crypts.(a–d) Light microscopy images from enclosed crypt; a large number of bacteria as observed in the crypts. L: lumen. (e) TEM of a crypt containing symbiotic bacteria. (f) TEM of a single symbiotic bacterium in the crypt.

Mentions: In order to see bacterial symbiont cells, we prepared thin transverse cross sections from the fourth midgut section of G. lineatum. Light microscopy (Fig. 2a–d) and TEM (Fig. 2e,f) observations revealed that a large number of rod-shape bacterial cells (≈1 μm) were harbored in the crypts of midgut. The bacterial symbionts were morphologically uniform bearing well-developed cell walls with two membranes, typical of gram-negative bacteria, but without obvious flagellum (Fig. 2c). Crypts were enclosed from the gut lumen, thereby maintaining the symbiont in the isolated cryptic cavities.


Gammaproteobacteria as essential primary symbionts in the striped shield bug, Graphosoma Lineatum (Hemiptera: Pentatomidae)
Light microscopy and transmission electron microscopy (TEM) of G. lineatum crypts.(a–d) Light microscopy images from enclosed crypt; a large number of bacteria as observed in the crypts. L: lumen. (e) TEM of a crypt containing symbiotic bacteria. (f) TEM of a single symbiotic bacterium in the crypt.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016839&req=5

f2: Light microscopy and transmission electron microscopy (TEM) of G. lineatum crypts.(a–d) Light microscopy images from enclosed crypt; a large number of bacteria as observed in the crypts. L: lumen. (e) TEM of a crypt containing symbiotic bacteria. (f) TEM of a single symbiotic bacterium in the crypt.
Mentions: In order to see bacterial symbiont cells, we prepared thin transverse cross sections from the fourth midgut section of G. lineatum. Light microscopy (Fig. 2a–d) and TEM (Fig. 2e,f) observations revealed that a large number of rod-shape bacterial cells (≈1 μm) were harbored in the crypts of midgut. The bacterial symbionts were morphologically uniform bearing well-developed cell walls with two membranes, typical of gram-negative bacteria, but without obvious flagellum (Fig. 2c). Crypts were enclosed from the gut lumen, thereby maintaining the symbiont in the isolated cryptic cavities.

View Article: PubMed Central - PubMed

ABSTRACT

Many members of suborder Heteroptra harbor heritable symbiotic bacteria. Here we characterize the gut symbiotic bacterium in Graphosoma lineatum (Hemiptera: Pentatomidae) by using molecular phylogeny, real-time PCR analysis as well as light and electron microscopy observations. The microscopy observations revealed the presence of a large number of rod-shaped bacterial cells in the crypts. A very high prevalence (98 to 100%) of the symbiont infection was found in the insect populations that strongly supports an intimate association between these two organisms. Real-time PCR analysis also showed that the Gammaproteobacteria dominated the crypts. The sequences of 16sr RNA and groEL genes of symbiont showed high levels of similarity (93 to 95%) to Pantoea agglomeranse and Erwinia herbicola Gammaproteobacteria. Phylogenetic analyses placed G. lineatum symbiont in a well-defined branch, divergent from other stink bug bacterial symbionts. Co-evolutionary analysis showed lack of host-symbiont phylogenetic congruence. Surface sterilization of eggs resulted in increased pre-adult stage in the offspring (aposymbionts) in comparison to the normal. Also, fecundity, longevity, and adult stage were significantly decreased in the aposymbionts. Therefore, it seems that the symbiont might play a vital function in the host biology, in which host optimal development depends on the symbiont.

No MeSH data available.


Related in: MedlinePlus