Snodgrassella alvi

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Snodgrassella alvi
Snodgrassella alvi, electron micrograph

Snodgrassella alvi , electron micrograph

Systematics
Department : Proteobacteria
Class : Betaproteobacteria
Order : Neisseriales
Family : Neisseriaceae
Genre : Snodgrassella
Type : Snodgrassella alvi
Scientific name of the  genus
Snodgrassella
Kwong & Moran, 2012
Scientific name of the  species
Snodgrassella alvi
Kwong & Moran , 2012

Snodgrassella alvi is a type of gram-negative bacteria within the Neisseriaceae and the only known species of the genus Snodgrassella . It wasisolated and scientifically describedin 2012 by Waldan K. Kwong and Nancy Moran , who named the bacteria after the American entomologist Robert Evans Snodgrass .

Snodgrassella alvi lives symbiotically as part of the intestinal flora in the midgut of honey bees ( Apis mellifera ) and some social bumblebee species . In this section of the intestine, they represent the dominant bacteria together with Gilliamella apicola , with both representing up to almost 40% of the local microflora. In the intestine, Snodgrassella alvi and Gilliamella apicola interact in the use of metabolic resources by using the metabolic products of the other species, and they settle accordingly in different areas of the intestinal wall.

According to a study published in September 2018, Snodgrassella alvi is harmed by the use of the plant protection product glyphosate , which leads to impairment of the intestinal microbiota. As a result, a weakening of the bees' resistance to harmful bacteria and the resulting weakening of the animals was observed. This effect was subsequently discussed in various international media as a possible cause of the bee mortality observed worldwide .

features

Appearance

Snodgrassella alvi is a type of bacteria and thus a unicellular organism without a nucleus (prokaryota). The individual cells are short and rod-shaped with a length of about 1.0 µm and a diameter of 0.4 µm. They are gram negative and accordingly only have a thin murein envelope .

Colonies of Snodgrassella alvi on blood agar

The bacteria are immobile and form colonies with other bacteria in the bays of the intestinal wall of the bee intestine. The strains can grow on blood agar , casein soy peptone agar (CASO or TSA), heart infusion agar (HIA) and LB medium (LBA) and after 2 days form smooth, white and round colonies with a diameter of about 1 millimeter or less.

Growth and metabolism

The species is microaerophilic , so it grows best in low oxygen levels. A five percent CO 2 atmosphere at a temperature of 37 ° C offers optimal growth conditions, while bacteria in the air or without oxygen ( anaerobia ) show only very weak growth or no growth at all. In the TSA, the growth range is around a pH value between 6.0 and 6.5. The catalase test and the test for nitrate reductases are positive, the oxidase test (detection of the enzyme cytochrome c oxidase ) is negative. Tests of the strains for β-glucosidase , β-galactosidase , indole production , proteolysis of gelatin and glucose fermentation are negative. They are not hemolytic and show variable responses to urease and arginine dihydrolase .

The bacterium can use citric and malic acid as the main source of carbon .

Chemotaxonomic Features

The combined proportion of cytosine and guanine ( GC content ) in the DNA is 41 to 43 mol%. The most important isoprenoid quinone is ubiquinone-10 . The main components of the fatty acids produced are palmitic acid (C 16: 0), cis-vaccenic acid (C 18: 1ω7 c / C 18: 1ω6 c) and lauric acid (C 12: 0), in which Snodgrassella alvi can be distinguished from closely related species.

Genome

The genome of Snodgrassela faeces has been fully sequenced . Of 2,226 protein- coding genes , 519 genes are essential and 399 genes are involved in colonization of honeybees.

Lifestyle and Physiology

Honey bee Honeybee anatomy
Snodgrassella alvi lives in the intestines of honey bees . Together with Gilliamella apicola , it dominates the ileum area (k) behind the midgut (i) and the pylorus (l)

Snodgrassella alvi lives in the intestines of honey bees and other representatives of the corbiculate bees. Similar strains in the genome were found in all of the species of the genera Apis (n = 6) and Bombus (n = 8) examined as well as in 9 of 13 examined species of stingless bees ( Meliponini ), but not in other animal species and outside their hosts proven. It is a key species in the honeybee intestine and dominates this microbiome together with seven other species, some of which have not yet been finally identified: Lactobacillus spp. Firm-4, Lactobacillus spp. Firm-5 (Phylum Firmicutes ), Bifidobacterium spp. (phylum Actinobacteria), Gilliamella apicola , Frischella perrara , Bartonella apis and Alpha 2.1 (Phylum Proteobacteria ). Together, these species make up 95% of intestinal bacteria. Snodgrassella alvi , Gilliamella apicola and Frischella perrara are considered to be species-specific key species.

Snodgrassella alvi and the gamma proteobacterium Gilliamella apicola dominate the area of ​​the ileum and colonize the inner wall of the intestine there. Only a few bacteria exist in the anterior area of ​​the intestine, while in the short area of ​​the pylorus Frischella perrara dominates and occurs almost exclusively there. In the rectum there are mainly Lactobacillus strains and Bifidobacterium .

In the case of social insects, the microbiome and, above all, the key species are passed on within the hive through the transmission of saliva and food. Bee larvae and young workers are almost free of intestinal bacteria in their first days of life and only acquire their normal microbial intestinal flora later orally through social interactions with other workers and through transmission between individuals within a beehive during mutual food transmission ( trophallax ) in the first days outside of the Honeycombs and at the beginning of their lives in the people. Although the larvae are also fed by female workers, their intestines, whose front and back are not connected before pupation , are almost free of bacteria. This is mainly attributed to a strong immune defense of the larvae and a bacteriocidal effect of the saliva of the feeding bees. Only after pupation and in the presence of nursing bees or the droppings of these bees do the young workers develop the intestinal flora typical of the hive. In contrast, when exposed only to the hive material such as honeycomb, honey and bee bread or only the bee saliva and trophallaxe of other bees, they develop atypical intestinal flora.

Within the intestine, the bacteria support the digestion of honey and pollen and also probably have a function in the immune defense against parasites and pathogenic bacteria. The protective effect of the natural bacterial composition could, among other things, be demonstrated against pathogens such as the unicellular organisms Crithidia bombi or Nosema bombi , which infect various bumblebee species, which lead to potentially fatal infections . However, excessive colonization of the bee intestine by Snodgrassella alvi can presumably disrupt the intestinal flora and increase susceptibility to infection with the trypanosome Lotmaria passim .

Interaction with Gilliamella apicola

Metabolic interactions between Gilliamella apicola and Snodgrassella alvi (simplified)

Within the bee intestine, the two dominant species Gilliamella apicola and Snodgrassella alvi occupy different areas of the intestine and different metabolic niches . Together they form a biofilm on the inner intestinal wall in which the colonies of Snodgrassella alvi sit directly on the intestinal wall and the colonies of Gilliamella apicola cover it.

Gilliamella apicola is a bacterium that breaks down sugar and produces carboxylic acids (saccharolytic fermenter), while Snodgrassella alvi oxidizes carboxylic acids . In the intestine, they form a network for the division of metabolic resources, in which both species benefit from the properties of the other. Gilliamella apicola converts simple carbohydrates (sugars) into energy through glycolysis and transfers the remaining molecules to Snodgrassella alvi , which has the necessary genes for the Krebs cycle and uses them, but cannot perform glycolysis. Both species also have numerous genes and proteins that enable intestinal colonization and interactions between the bacterial cells.

Variations in these genes could explain the host fidelity of the strains observed in previous phylogenetic studies. Snodgrassella alvi strains can colonize their ancestral bee host, but not bees of another genus. In accordance with the specific, long-term host association, a comparative genomic analysis revealed large differences and little or no gene flow between intestinal symbionts of bumblebees and bees. However, within one host type ( Apis or Bombus ), researchers discovered signs of horizontal gene transfer between Gilliamella apicola and Snodgrassella alvi , demonstrating the importance of the broader intestinal community in directing the evolution of individual members. The results indicated that host specificity is likely to be influenced by several factors, including direct interactions of the bacteria with the hosts, microbe-microbe interactions, and social transmission of the intestinal flora.

Effects of antibiotics and glyphosate

The effects of various substances on the bees' intestinal flora have only been researched selectively. Studies are available on the effect of antibiotics and glyphosate on the bacterial flora and, above all, on the colonization by Gilliamella apicola and Snodgrassella alvi .

In 2017, Kasie Raymann and colleagues examined the effect of the antibiotic tetracycline , which is sometimes used in beehives to prevent bacterial infections in bee larvae, on the bees' intestinal flora. They found that the treatment resulted in a reduction in the number of Snodgrassella alvi cells , while the number of cells in Gilliamella apicola was barely reduced. In a second study, however, they were able to determine that there was a shift in the genotypes in Gilliamella apicola in favor of antibiotic- resistant cells and thus a reduction in genetic diversity, while the genetic diversity in Snodgrassella alvi was not impaired. According to their investigations, exposure to antibiotics also led to a reduced survival rate of the bees treated with them, both in the beehive and in laboratory experiments in which the bees were exposed to opportunistic bacterial pathogens.

It is generally assumed that the herbicide glyphosate is harmless to animals, including bees and other insects, as its effects target the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which is only found in plants and microorganisms. The effects of glyphosate on the microbiomes of the animals and thus also the microorganisms that colonize the bees' intestines and represent the natural intestinal flora there have not yet been considered with this assumption. The gene encoding EPSPS is present in almost all sequenced genomes of bee intestinal bacteria, suggesting that these are potentially susceptible to glyphosate. According to a study published in September 2018, glyphosate affects the gut microbiota of young honey bees by inhibiting the shikimic acid pathway , especially in Snodgrassella alvi . The exposure of bees to glyphosate changes the intestinal flora of young bee workers, at least experimentally, and thus increases the bees' susceptibility to infections. As a result, a weakening of the resistance to opportunistic pathogens and especially the harmful bacterial species Serratia marcescens has been observed, which is associated with an increased mortality of bees. This effect was discussed in the press as a possible cause of the international bee deaths. u. a. However, resistance of some strains of Snodgrassella alvi to glyphosate has also been described.

Use for mite defense and protection against infection

Varroa mite on a bee in the scanning electron microscope

In January 2020, the results of research were published in the genetically modified alvi Snodgrassella were used to the immune system of bees to attack by the Varroa mite ( Varroa destructor ) strengthen and this induced viral infections. The team modified the bacteria so that a built-in plasmid produced labeled double-stranded RNA ( dsRNA ). The dsRNA module can be used specifically to interfere with specific bee genes as well as with important virus and mite genes. In the laboratory, the gene expression of the selected area could be blocked for at least 15 days if the modified bacteria established themselves in the bee intestine and the dsRNA was continuously expressed. As an effect, the survival of the varroa mites on the bees was reduced and the transmission and infection with the wing deformation virus was inhibited.

Taxonomy

External system

Snodgrassella alvi was isolated from the intestines of the European honey bee by Waldan K. Kwong and Nancy A. Moran together with Gilliamella apicola and described scientifically in 2012. Vincent G. Martinson and colleagues, also in the working group of Nancy A. Moran, identified both species beforehand and provisionally named Candidatus Snodgrassella alvi and Gilliamella apicola . The genus Snodgrassella was named after the American entomologist Robert Evans Snodgrass , who was honored as a pioneer in researching insect physiology in the early 20th century, while the specific epithet "alvi" refers to the lacunae of the bees' intestines. The type strain is wkB2 T (= NCIMB 14803 T = ATCC BAA-2449 T = NRRL B-59751 T) isolated from the intestines of the western honey bee ( A. mellifera ) in Connecticut , United States.



 Leeia oryzae


   

 Genera Amantichitinum , Chitiniphilus , Andreprevotia , Deefgia , Chitinibacter , Chitinilyticum


   

 Genera Aquaspirillium , Microvirgula , Laribacter


   

 Genera Gulbenkiania , Pseudogulbenkiania , Vogesella , Chromobacterium


   

 Vitreoscilla


   


  Snodgrassella alvi


   

 Stenoxybacter acetivorans



   

Genera Neisseria , Eike Ella , Conchiformibius , Alysiella , Simonsiella , Kling Ella , Bergeriella








Template: Klade / Maintenance / Style

Phylogenetic position of Snodgrassella alvi according to Kwong 2017

The bacteria are classified as Betaproteobacteria within the Neisseriaceae and are related to similar bacteria from the intestines of termites or other insects. In 2017, Kwong created a cladogram of the Neisseriaceae on the basis of published genomic data , in which he classified Snodgrassella alvi as a sister species of the species Stenoxybacter acetivorans that occurs in the intestines of termites and, together with the genus Vitreoscilla, at the base of a taxon from the genera Neisseria ( polyphyletic ), Eikenella , Conchiformibius , Alysiella , Simonsiella , Kling Ella and Bergeriella placed. While the more basal taxa occur mainly in open habitats such as in the ground or in water, the derived forms including Stenoxybacter and Snodgrassella are usually linked to other organisms, especially animals.

A working group led by the Chinese researcher Yong Li grouped Vitreoscilla , Stenoxybacter and Snodgrassella in a taxon that in addition, the newly described in the work type Populibacter corticis from the bark of a tree cancer of the bastard black poplar ( Populus x euramericana ) as a sister species of Snodgrassella alvi contains.

Strains and host specificity

Within the species, the bacteria are classified according to strains taken from different hosts . The strain wkB2 T used for the first description was correspondingly isolated from the intestine of the western honey bee ( Apis mellifera ) in Connecticut, United States. As a specialized Darmsymbiont developed to Snodgrassella faeces for millions of years with honey bees and bumblebees (genus Bombus ) are where to find the bacteria.

During investigations it was found that the different strains of Snodgrassella alvi from honey bees worldwide hardly differ in the gene sequences of the 16S rRNA (in the V4 region ) and are almost identical. In contrast, there are differences in the single-copy gene minD (an ATPase that inhibits cell division ), especially in strains of Snodgrassella alvi from honey bees, while bumblebees only have one strain of Snodgrassella alvi . When comparing Snodgrassella alvi strains from honey bees with those from different bumblebee species, it was found on the one hand that the genetic variability within the individual honeybees in a hive is significantly higher than in the bumblebees of a colony, with the diversity being due to the establishment of a bee colony Flocks of workers as opposed to a single bumble bee. As a result, the intestines of the individual honey bees are usually (86%) colonized by several strains of Snodgrassella alvi , while that of the bumblebees usually (72%) only contains one strain. In addition, a host specificity of the bacteria of the honeybees was determined in which there are no strains that can be found in both honeybees and bumblebee species. Within the bumblebees there are some Snodgrassella alvi strains that occur species- or sub-genus-specific, while others occur in several species of different sub-genera. Further analyzes showed that the protein-coding genes of the honeybee strains of Snodgrassella alvi differ significantly from those of the rRNA. This is explained by the fact that the variability of the 16S rRNA loci has been restricted by frequent recombination within the populations, while other regions of the genome continuously develop and diversify in adaptation to changing ecological conditions in the intestine.

supporting documents

  1. ↑ a b c d Erick VS Motta, Kasie Raymann, Nancy A. Moran: Glyphosate perturbs the gut microbiota of honey bees. In: Proceedings of the National Academy of Sciences 115 (41), 2018; Pp. 10305-10310. doi : 10.1073 / pnas.1803880115 .
  2. ↑ a b c d e f g h Waldan K. Kwong, Nancy A. Moran: Cultivation and characterization of the gut symbionts of honey bees and bumble bees: description of Snodgrassella alvi gen. Nov., Sp. nov., a member of the family Neisseriaceae of the Betaproteobacteria, and Gilliamella apicola gen. nov., sp. nov., a member of Orbaceae fam. nov., Orbales ord. nov., a sister taxon to the order 'Enterobacteriales' of the Gammaproteobacteria. International Journal of Systematic and Evolutionary Microbiology, Volume 63, 6, October 5, 2012, doi : 10.1099 / IJS.0.044875-0 .
  3. ↑ a b Yong Li, Han Xue, Sheng-qi Sang, Cai-li Lin, Xi-zhuo Wang: Phylogenetic analysis of family Neisseriaceae based on genome sequences and description of Populibacter corticis gen. Nov., Sp. nov., a member of the family Neisseriaceae, isolated from symptomatic bark of Populus × euramericana canker. Plos One, April 13, 2017. doi : 10.1371 / journal.pone.0174506 .
  4. ↑ a b c d e f Waldan K. Kwong, Philipp Engel, Hauke ​​Koch, Nancy A. Moran: Genomics and host specialization of honey bee and bumble bee gut symbionts. Proceedings of the National Academy of Sciences 111 (31), Aug. 5, 2014; Pp. 11509-11514. doi : 10.1073 / pnas.1405838111 .
  5. ↑ 597812552 - Nucleotide Result. In: ncbi.nlm.nih.gov. Retrieved May 20, 2019 .
  6. ↑ JE Powell, SP Leonard, WK Kwong, P. Engel, NA Moran: Genome-wide screen identifies host colonization determinants in a bacterial gut symbiont. In: Proceedings of the National Academy of Sciences . Volume 113, number 48, 11 2016, pp. 13887-13892, doi: 10.1073 / pnas.1610856113 , PMID 27849596 , PMC 5137728 (free full text).
  7. ↑ Waldan K. Kwong, Luis A. Medina, Hauke ​​Koch, Kong-Wah Sing, Eunice Jia Yu Soh, John S. Ascher, Rodolfo Jaffé, Nancy A. Moran: Dynamic microbiome evolution in social bees. Science Advances 3 (3), 2017: e1600513. doi: 10.1126 / sciadv.1600513
  8. ^ A b c Elijah Powell, Vincent G. Martinson, Katherine Urban-Mead, Nancy A. Moran: Routes of Acquisition of the Gut Microbiota of the Honey Bee Apis mellifera. In: Applied and Environmental Microbiology 80, 2014; Pp. 7378-7387. doi : 10.1128 / AEM.01861-14 .
  9. ↑ Waldan K. Kwong, Nancy A. Moran: Well microbial communities of social bees. Nature Reviews Microbiology 14, 2016; Pp. 374-384. doi : 10.1038 / nrmicro.2016.43 .
  10. ^ A b c Vincent G. Martinson, Jamie Moy, Nancy A. Moran: Establishment of Characteristic Gut Bacteria during Development of the Honeybee Worker. Applied and Environmental Microbiology 78, 2012; Pp. 2830-2840. doi : 10.1128 / AEM.07810-11 .
  11. ↑ P. Engel, Nancy A. Moran: The gut microbiota of insects - diversity in structure and function. In: FEMS Microbiology Reviews, 37 (5), 699-735, September 1, 2013. doi : 10.1111 / 1574-6976.12025 .
  12. ↑ Hauke ​​Koch, Paul Schmid-Hempel: Socially transmitted gut microbiota protect bumble bees against an intestinal parasite. In: Proceedings of the National Academy of Sciences 108 (48), 2011, pp. 19288-19292. doi : 10.1073 / pnas.1110474108 .
  13. ↑ Daniel P. Cariveau, J. Elijah Powell, Hauke Koch, Rachael Winfree, Nancy A. Moran: Variation in good microbial communities and its association with pathogen infection in wild bumble bees (Bombus). The ISME Journal 8, 2014; Pp. 2369-2379. doi : 10.1038 / ismej.2014.68 .
  14. ^ RS Schwarz, NA Moran, JD Evans: Early gut colonizers shape parasite susceptibility and microbiota composition in honey bee workers. In: Proceedings of the National Academy of Sciences . Volume 113, number 33, 08 2016, pp. 9345-9350, doi : 10.1073 / pnas.1606631113 , PMID 27482088 , PMC 4995961 (free full text).
  15. ↑ Lucie Kešnerová, Ruben AT Mars, Kirsten M. Ellegaard, Michaël Troilo, Uwe Sauer, Philipp Engel: Disentangling metabolic functions of bacteria in the honey bee gut. Plos One, December 12, 2017. doi : 10.1371 / journal.pbio.2003467
  16. ↑ a b Kasie Raymann, Louis-Marie Bobay, Nancy A. Moran: Antibiotics reduce genetic diversity of species in the core honeybee microbiome good. Molecular Ecology 27 (8), November 22, 2017. doi : 10.1111 / mec.14434 .
  17. ↑ a b Kasie Raymann, Zack Shaffer, Nancy A. Moran: Antibiotic exposure perturbs the gut microbiota and elevates mortality in honeybees. Plos One, March 14, 2017. doi : 10.1371 / journal.pbio.2001861 .
  18. ↑ Frank Patalong: Glyphosate is said to be the cause of bee deaths. Spiegel online, September 24, 2018; accessed on March 31, 2019.
  19. ↑ Ashley May: Honey bees are dying. A popular weed killer might be to blame, study says. USA today, September 25, 2018; accessed on March 31, 2019.
  20. ↑ Damian Carrington: Monsanto's global weedkiller harms honeybees, research finds. The Guardian, September 24, 2018; accessed on March 31, 2019.
  21. ↑ Tina Baier: Does glyphosate make bees sick? Süddeutsche Zeitung, September 25, 2018; accessed on March 31, 2019.
  22. ^ A b Sean P. Leonard, J. Elijah Powell, Jiri Perutka, Peng Geng, Luke C. Heckmann, Richard D. Horak, Bryan W. Davies, Andrew D. Ellington, Jeffrey E. Barrick, Nancy A. Moran: Engineered symbionts activate honey bee immunity and limit pathogens. Science 367 (6477), Jan. 31, 2020; Pp. 573-576. doi : 10.1126 / science.aax9039 .
  23. ↑ WK Kwong, NA Moran: Cultivation and characterization of the gut symbionts of honey bees and bumble bees: description of Snodgrassella alvi gen. Nov., Sp. nov., a member of the family Neisseriaceae of the Betaproteobacteria, and Gilliamella apicola gen. nov., sp. nov., a member of Orbaceae fam. nov., Orbales ord. nov., a sister taxon to the order 'Enterobacteriales' of the Gammaproteobacteria. In: International journal of systematic and evolutionary microbiology. Volume 63, Pt 6 June 2013, pp. 2008-2018, doi : 10.1099 / ijs.0.044875-0 , PMID 23041637 .
  24. ↑ a b c Waldan K. Kwong: Whole genome phylogeny of Neisseriaceae species . Blog post in Waldan K. Kwong's blog, May 13, 2017; accessed on March 1, 2019.
  25. ↑ Waldantgu K. Kwong, Hao Zheng, Nancy A. Moran: Convergent evolution of a modified, acetate-driven TCA cycle in bacteria. Nature Microbiology 2, 2017; Article 17067. doi : 10.1038 / nmicrobiol.2017.67 .
  26. ^ A b c Elijah Powell, Nalin Ratnayeke Nancy A. Moran: Strain diversity and host specificity in a specialized gut symbiont of honeybees and bumblebees. Molecular Ecology 25 (18) September 2016; Pp. 4461-4471. doi : 10.1111 / mec.13787 .
  27. ↑ Philipp Engel, Ramunas Stepanauskas, Nancy A. Moran: Hidden Diversity in Honey Bee Gut Symbionts Detected by Single-Cell Genomics. PLOS Genetics, September 11, 2014. doi : 10.1371 / journal.pgen.1004596 .

literature

  • Waldan K. Kwong, Nancy A. Moran: Cultivation and characterization of the gut symbionts of honey bees and bumble bees: description of Snodgrassella alvi gen. Nov., Sp. nov., a member of the family Neisseriaceae of the Betaproteobacteria, and Gilliamella apicola gen. nov., sp. nov., a member of Orbaceae fam. nov., Orbales ord. nov., a sister taxon to the order 'Enterobacteriales' of the Gammaproteobacteria. International Journal of Systematic and Evolutionary Microbiology, Volume 63, 6, October 5, 2012, doi : 10.1099 / IJS.0.044875-0 .

Web links

Commons : Snodgrassella alvi  - collection of images, videos and audio files
This version was added to the list of articles worth reading on July 3, 2020 .