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Bacterial Infection and Immune Responses in Lutzomyia longipalpis Sand Fly Larvae Midgut.

Heerman M, Weng JL, Hurwitz I, Durvasula R, Ramalho-Ortigao M - PLoS Negl Trop Dis (2015)

Bottom Line: Depending on the aspects of their development, insects can acquire microbes present in soil, water, and plants.Sand fly larval stages acquire microorganisms from the soil, and the abundance and distribution of these microorganisms may vary depending on the sand fly species or the breeding site.Moreover, bacterial distribution, and likely the ability to colonize the gut, is driven, at least in part, by a gradient of pH present in the gut.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Kansas State University, Manhattan, Kansas, United States of America.

ABSTRACT
The midgut microbial community in insect vectors of disease is crucial for an effective immune response against infection with various human and animal pathogens. Depending on the aspects of their development, insects can acquire microbes present in soil, water, and plants. Sand flies are major vectors of leishmaniasis, and shown to harbor a wide variety of Gram-negative and Gram-positive bacteria. Sand fly larval stages acquire microorganisms from the soil, and the abundance and distribution of these microorganisms may vary depending on the sand fly species or the breeding site. Here, we assess the distribution of two bacteria commonly found within the gut of sand flies, Pantoea agglomerans and Bacillus subtilis. We demonstrate that these bacteria are able to differentially infect the larval digestive tract, and regulate the immune response in sand fly larvae. Moreover, bacterial distribution, and likely the ability to colonize the gut, is driven, at least in part, by a gradient of pH present in the gut.

No MeSH data available.


Related in: MedlinePlus

Infection of sand fly larva midgut by B. subtilis and P. agglomerans.EGFP- or GFP-expressing Bs and Pa were grown on LB-agar plates with selective media and fed to 3rd instar sand fly larvae. Larvae guts were dissected and assessed for the distribution of each bacterium. In A, a schematic representation of the sand fly larval gut. Ingested food is moved from right (proventriculus–pv) to left, towards to posterior midgut and hindgut. Confocal images (1024x1024 per tile pixel resolution) of the distribution of EGFP-expressing Bs-infected and GFP-expressing Pa-infected midguts are shown in panels B and C. Posterior (pos) and anterior (ant) portions of midguts are indicated. SG, salivary glands. Inset in 1C: blow up of area of gut delineated by a rectangle (asterisk) showing biofilm formed in Pa infection. Bars = 100 µm.
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pntd.0003923.g001: Infection of sand fly larva midgut by B. subtilis and P. agglomerans.EGFP- or GFP-expressing Bs and Pa were grown on LB-agar plates with selective media and fed to 3rd instar sand fly larvae. Larvae guts were dissected and assessed for the distribution of each bacterium. In A, a schematic representation of the sand fly larval gut. Ingested food is moved from right (proventriculus–pv) to left, towards to posterior midgut and hindgut. Confocal images (1024x1024 per tile pixel resolution) of the distribution of EGFP-expressing Bs-infected and GFP-expressing Pa-infected midguts are shown in panels B and C. Posterior (pos) and anterior (ant) portions of midguts are indicated. SG, salivary glands. Inset in 1C: blow up of area of gut delineated by a rectangle (asterisk) showing biofilm formed in Pa infection. Bars = 100 µm.

Mentions: A scheme representing the anatomy of L. longipalpis sand fly 3rd instar (L3) gut is depicted in Fig 1A. Following continuous feeding of LB-agar containing EGFP-expressing Bs to larvae, a pervasive signal was found across the entire length of the midgut for infected insects as depicted by the fluorescent signal of full length images of the gut (Fig 1B and S2A Fig and S1 Video). However, when the GFP-expressing Pa was fed to larvae in a similar manner the bacteria were mostly localized to a narrow area of the posterior portion of the midgut (Fig 1C and S2B Fig), and were only found on the apical surface of the midgut lumen (S2 Video). Also observed were areas of higher intensity GFP signal in Pa-infected guts, suggesting the presence of biofilm (Fig 1C). A less pronounced GFP signal in Pa fed was also observed in the proventriculus of the gut (Fig 1C). Infection rates as determined by a qualitative assessment of the GFP signal within the midgut of the larvae following continuous feeding are described in Table 1.


Bacterial Infection and Immune Responses in Lutzomyia longipalpis Sand Fly Larvae Midgut.

Heerman M, Weng JL, Hurwitz I, Durvasula R, Ramalho-Ortigao M - PLoS Negl Trop Dis (2015)

Infection of sand fly larva midgut by B. subtilis and P. agglomerans.EGFP- or GFP-expressing Bs and Pa were grown on LB-agar plates with selective media and fed to 3rd instar sand fly larvae. Larvae guts were dissected and assessed for the distribution of each bacterium. In A, a schematic representation of the sand fly larval gut. Ingested food is moved from right (proventriculus–pv) to left, towards to posterior midgut and hindgut. Confocal images (1024x1024 per tile pixel resolution) of the distribution of EGFP-expressing Bs-infected and GFP-expressing Pa-infected midguts are shown in panels B and C. Posterior (pos) and anterior (ant) portions of midguts are indicated. SG, salivary glands. Inset in 1C: blow up of area of gut delineated by a rectangle (asterisk) showing biofilm formed in Pa infection. Bars = 100 µm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495979&req=5

pntd.0003923.g001: Infection of sand fly larva midgut by B. subtilis and P. agglomerans.EGFP- or GFP-expressing Bs and Pa were grown on LB-agar plates with selective media and fed to 3rd instar sand fly larvae. Larvae guts were dissected and assessed for the distribution of each bacterium. In A, a schematic representation of the sand fly larval gut. Ingested food is moved from right (proventriculus–pv) to left, towards to posterior midgut and hindgut. Confocal images (1024x1024 per tile pixel resolution) of the distribution of EGFP-expressing Bs-infected and GFP-expressing Pa-infected midguts are shown in panels B and C. Posterior (pos) and anterior (ant) portions of midguts are indicated. SG, salivary glands. Inset in 1C: blow up of area of gut delineated by a rectangle (asterisk) showing biofilm formed in Pa infection. Bars = 100 µm.
Mentions: A scheme representing the anatomy of L. longipalpis sand fly 3rd instar (L3) gut is depicted in Fig 1A. Following continuous feeding of LB-agar containing EGFP-expressing Bs to larvae, a pervasive signal was found across the entire length of the midgut for infected insects as depicted by the fluorescent signal of full length images of the gut (Fig 1B and S2A Fig and S1 Video). However, when the GFP-expressing Pa was fed to larvae in a similar manner the bacteria were mostly localized to a narrow area of the posterior portion of the midgut (Fig 1C and S2B Fig), and were only found on the apical surface of the midgut lumen (S2 Video). Also observed were areas of higher intensity GFP signal in Pa-infected guts, suggesting the presence of biofilm (Fig 1C). A less pronounced GFP signal in Pa fed was also observed in the proventriculus of the gut (Fig 1C). Infection rates as determined by a qualitative assessment of the GFP signal within the midgut of the larvae following continuous feeding are described in Table 1.

Bottom Line: Depending on the aspects of their development, insects can acquire microbes present in soil, water, and plants.Sand fly larval stages acquire microorganisms from the soil, and the abundance and distribution of these microorganisms may vary depending on the sand fly species or the breeding site.Moreover, bacterial distribution, and likely the ability to colonize the gut, is driven, at least in part, by a gradient of pH present in the gut.

View Article: PubMed Central - PubMed

Affiliation: Department of Entomology, Kansas State University, Manhattan, Kansas, United States of America.

ABSTRACT
The midgut microbial community in insect vectors of disease is crucial for an effective immune response against infection with various human and animal pathogens. Depending on the aspects of their development, insects can acquire microbes present in soil, water, and plants. Sand flies are major vectors of leishmaniasis, and shown to harbor a wide variety of Gram-negative and Gram-positive bacteria. Sand fly larval stages acquire microorganisms from the soil, and the abundance and distribution of these microorganisms may vary depending on the sand fly species or the breeding site. Here, we assess the distribution of two bacteria commonly found within the gut of sand flies, Pantoea agglomerans and Bacillus subtilis. We demonstrate that these bacteria are able to differentially infect the larval digestive tract, and regulate the immune response in sand fly larvae. Moreover, bacterial distribution, and likely the ability to colonize the gut, is driven, at least in part, by a gradient of pH present in the gut.

No MeSH data available.


Related in: MedlinePlus