View source for Snodgrassella alvi wkB2

{{Uncurated}}
[[File:s_mg.jpg|500px|thumb|right|Figure 1: A transmission electron micrograph (TEM) of <i> S. alvi </i> wkB2 cells were found to be approximately 1.0µm long and 0.4 µm wide [4].]]
==Classification==

===Taxonomy===

Domain: Bacteria <br>
:Phylum: Proteobacteria <br>
::Class: Betaproteobacteria <br>
:::Order: Neisseriales <br>
::::Family: Neisseriaceae <br>
:::::Genus: <i> Snodgrassella </i> <br>
::::::Species: <i> alvi </i> <br>
:::::::Strain: wkB2 <br>

{|
| height="10" bgcolor="#FFDF95" |
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''
|}

===Names===

''Snodgrassella alvi'' wkB2<br>
''Candidatus Snodgrassella alvi'' wkB2 (previously)<br>
''S. alvi'' wkB2 <br>

==Description and Significance==

<i> S. alvi </i> wkB2 is a core member of the western honey bee (<i> Apis mellifera </i>) worker gut microbiota [7]. The cells are short gram negative rods. On agar, <i> S. alvi </i> wkB2 forms smooth white round colonies [4]. It is a is non-motile biofilm former colonizing the ileum of <i> A. mellifera </i> [4]. 

<i> Snodgrassella </i> was so named in honor of Robert Evans Snodgrass who was a prominent figure studying insect physiology and had described <i> Apis mellifera </i> [6]. <i> alvi </i> refers to the latin word "alvus" which refers to the bowels or to bees [6]. The strain was described by Waldon Kwong who's initials are "w.k."

Initially, the name "Candidatus" was added to the front of <i> Snodgrassella alvi </i> because its discovery was through gene sequencing and had not been cultivated yet [6].

==Genome Structure==
[[File:S.alvi.jpg|450px|thumb|right|Figure 2: <i> S. alvi </i> genome shown to the right. The protein coding regions are plotted clockwise in solid red (darker red + strand and lighter red - strand). <i> S. alvi </i> wkB2 G+C skew is shown on the outer edge [3].]] 

===Genome===
The genome of <i> S. alvi </i> wkB2 consists of a singular circular chromosome containing 2,527,978 bp [3]. The G+C content is 41.3% [3]. 

Some pieces of the genome have mutated over time and lost function as <i> S. alvi </i> wkB2 is an obligate symbiont of 
<i> A. mellifera </i> and is believed to have co-evolved [3]. <i> S. alvi </i> wkB2 is also beleived to engage in Horizontal
Gene Transfer (HGT) with a proximal gut inhabitant of <i>A. mellifera</i>, <i> Gilliamella apicola </i>. 

====Annotated Genes====

There are 2295 annotated genes and 2193 of them are protein coding, 76 are non-coding, the rest (26) are pseudogenes [8]. 

A few notable annotated gene functions include genes that code for many pathogen associated functions. One gene codes for 
nonribosomal peptide synthesis of siderophores and one that codes for type 6 secretion system (T6SS) [3].

<br>
<br>

==Cell Structure, Metabolism and Life Cycle==

===Cell Structure===
[[File:S_alvi_metabolism.jpg|570px|thumb|right|Figure 3: The blue image shows <i> S. alvi </i> metabolic pathways predicted from genome sequencing. The solid circles are specific to the <i> S. alvi </i> wkB2 and wkB1 strains. Green lines indicate possible interactions between <i> G. apicola </i> and <i> S. alvi </i> [3].]] 
<i> S. alvi </i> wkB2 is gram negative, non-motile rod [4]. It displays a type IV pilli structure and YadA-like adhesins which are used to interact with the host gut epithelium which can be seen in figure 3. A TEM of <i> S. alvi </i> wkB2 can be seen in figure 1.

===Metabolism===

<i> S. alvi </i> wkB2 is an obligate aerobe. <i> S. alvi </i> wkB2 has transportation systems for taking up carboxylates like citrate, malate, & α-ketoclutarate [3]. These can then be used in the TAC cycle [3]. Transportation systems within <i> S. alvi </i> wkB2 can also allow for the uptake of lactate which can be directly converted into pyruvate through the enzyme, lactate dehydrogenase [3]. 

A TCA cycle enzyme, succinyl-CoA synthetase, which catalyzes the interconversion of succinyl-CoA and succinate, is not present in <i> S. alvi </i> yet the pathway is considered to still be functional as no alternative pathways exist to bypass the TCA cycle [3].

<i> S. alvi </i> is able to synthesize purine and pyrimidine nucleotides as well as all 21 proteinogenic amino acids (except selenocysteine). Vitamin B2 and B6 can be synthesized. <i> S. alvi </i> wkB2 specifically can synthesize B3 and its derivatives (NAD+ and NADP+) from aspartate [3]. 

====Lost Metabolic Pathways====

Evidence has been found suggesting that <i> S. alvi </i> was able to take up and break down carbohydrates, but has since lost that ability [3]. The Glycolosis pathway, Pentose phosphate pathway, & Entner-Doudoroff pathway have all lost essential enzymes [3]. These pathways are typically used to convert sugars to pyruvate. 


====Biochemical Tests====

      Nitrate reductase: Positive 
               Catalase: Positive 
                 Urease: Positive 
   Cytochrome C Oxidase: Negative 
          β-Glucosidase: Negative 
      Indole production: Negative 
             Gelatinase: Negative 
        β-Galactosidase: Negative 
   Arginine dihydrolase: Negative 
         H2S production: Negative 
             Haemolysis: Negative <br>
  The above data was from the initial cultivation-based characterization of <i> S. alvi </i> wkB2 [4].

===Life Cycle===

<i> S. alvi </i> wkB2 lives its entire natural life within the gut of <i> A. mellifera </i> worker bees. Cultivation of <i> S. alvi </i> wkB2 in vivo needs no substrate or assistance outside of the bee's regular diet. It is primarily passed on through the fecal-oral route but can also be passed on from surfaces or bee socialization [6].

This strain can also be cultivated in vitro on the following agars: Heart Infusion, Heart Infusion supplemented with Sheep's Blood, Columbia supplemented with Sheep's Blood (CBA), & R2 agar [1]. Liquid cultivation of <i> S. alvi </i> wkB2 is typically in Insectargro, Salt-free LB, or R2 Liquid Media [1]. 

On solid or liquid media, in vitro cultivation of <i> S. alvi </i> wkB2 is typically at 35°C and 5% CO2 [1].

==Ecology==
[[File:gut_location.jpg|450px|thumb|right|Figure 4: The composition of the typical adult worker bee based on 16S rRNA gene amplicons from whole guts. The localization was determined based on fluorescence in situ hybridization and qPCR studeies. <i> S. alvi </i> is shown in green [5].]] 
===Bee Gut Importance===
Within the bee gut, <i> S. alvi </i> wkB2 plays a vital role in O2 consumption keeping the gut of the bee anaerobic [5]. <i> S. alvi </i> wkB2 is also a primary biofilm former, forming a layer around the ileum which can be seen in figure 4 [5].

<i> S. alvi </i> wkB2 is able to occupy a very important niche within the bee gut, using carboxylates rather than carbohydrates suggesting that it has synergistic interactions with other native gut dwelling microbes which secrete this carboxylates [3]. However, <i> S. alvi </i> wkB2 is able to colonize and thrive within <i> A. mellifera </i> on its own.

===Ecological Importance===

For <i> A. mellifera </i> two pests that have been attributed to the large decline in honey bee populations are, the Varroa mite (<i>Varroa destructor</i>) and the Deformed Wing Virus (DWV) [2].

A transformed <i> S. alvi </i> wkB2 cells using RNAi have been proposed as a solution to the decreasing honey bee population [2]. It has been shown that these synthetic <i> S. alvi </i> wkB2 cells can sucessfully colonize <i> A. mellifera </i> in the same part of the ileum that it usually occupies [2][5]. <br>

This engineered microbe was transformed with a plasmid coding for double stranded RNA (dsRNA) targeting an essential mRNA on the deformed wing virus which plagues the western honey bee [2]. Leonard et al. were able to show an increase in bee survival for bees incoulated with the DWV and had sucessful colonizations of transformed <i> S. alvi </i> wkB2 cells [2].In another experiment, <i> S. alvi </i> wkB2 was transformed with a plasmid which coded for dsRNA which targeted 14 essential Varroa mite genes. They were also able to show a decrease in survival rates for the Varroa mites feeding on these bees [2].

Synthetically engineered <i> S. alvi </i> wkB2 after further testing and ethical consideration may be able to be implemented in the environment as a solution to protect the decreasing bee population.

==References==
[Sample reference] [http://ijs.sgmjournals.org/cgi/reprint/50/2/489 Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "''Palaeococcus ferrophilus'' gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". ''International Journal of Systematic and Evolutionary Microbiology''. 2000. Volume 50. p. 489-500.]

[1] Barricklab.org. 2020. Barrick Lab :: Protocolsculturingsnodgrassellaalvi. [online] Available at: <https://barricklab.org/twiki/bin/view/Lab/ProtocolsCulturingSnodgrassellaAlvi> [Accessed 29 April 2020].

[2] Leonard, S., Powell, J., Perutka, J., Geng, P., Heckmann, L., Horak, R., Davies, B., Ellington, A., Barrick, J. and Moran, N., 2020. Engineered symbionts activate honey bee immunity and limit pathogens. Science, 367(6477), pp.573-576.

[3] Kwong, W., Engel, P., Koch, H. and Moran, N., 2014. Genomics and host specialization of honey bee and bumble bee gut symbionts. Proceedings of the National Academy of Sciences, 111(31), pp.11509-11514.

[4] Kwong, W. and Moran, N., 2012. 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, 63(Pt 6), pp.2008-2018.

[5] Kwong, W. and Moran, N., 2016. Gut microbial communities of social bees. Nature Reviews Microbiology, 14(6), pp.374-384.

[6] Martinson, V., Moy, J. and Moran, N., 2012. Establishment of Characteristic Gut Bacteria during Development of the Honeybee Worker. Applied and Environmental Microbiology, 78(8), pp.2830-2840.

[7] Moran, N., Hansen, A., Powell, J. and Sabree, Z., 2012. Distinctive Gut Microbiota of Honey Bees Assessed Using Deep Sampling from Individual Worker Bees. PLoS ONE, 7(4), p.e36393.

[8] Ncbi.nlm.nih.gov. 2020. Home - Gene - NCBI. [online] Available at: <https://www.ncbi.nlm.nih.gov/gene> [Accessed 29 April 2020].

==Author==
Page authored by Samantha Worthington, student of Prof. Jay Lennon at Indiana University.

<!-- Do not remove this line-->[[Category:Pages edited by students of Jay Lennon at Indiana University]]