Name: an improved chemotaxis assay for the rapid identification of rhizobacterial chemoattractants in root exudates
Uploaded: 2022-03-25T13:30:00
Description: Watch this Scientific Journal Video about An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates at JoVE.com

This work was supported by the National Natural Science Foundation of China (Nos. 31870493), the Key Research and Development Projects in Heilongjiang, China (GA21B007), and the Basic Research Fees of Universities in Heilongjiang Province, China (No. 135409103).

1. Materials and equipment
NOTE: Bacillus altitudinis LZP02 (CP075052) was isolated from the rhizosphere of rice in northeast China12,13 for this study.
<ol>
	<li>Culture B. altitudinis LZP02 in Luria-Bertani (LB) medium (peptone, 10 g L-1; NaCl, 8 g L-1 and yeast extract, 5 g L-1) for 10 h. Collect cells by centrifugation at 9,569 x g for 2 min at ...

<ol>
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M., Joshi, P., Belwalkar, M., Archana, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Root+exudates+influence+chemotaxis+and+colonization+of+diverse+plant+growth-promoting+rhizobacteria+in+the+Cajanus+cajan+-+Zea+mays+intercropping+system.">Root exudates influence chemotaxis and colonization of diverse plant growth-promoting rhizobacteria in the Cajanus cajan - Zea mays intercropping system.</a> Rhizosphere. 18 (12), 100331 (2021).</li><li>Sampedro, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+halophyte+root+exudates+and+their+components+on+chemotaxis,+biofilm+formation+and+colonization+of+the+halophilic+bacterium+halomonas+anticariensis+FP35T.">Effects of halophyte root exudates and their components on chemotaxis, biofilm formation and colonization of the halophilic bacterium halomonas anticariensis FP35T.</a> Microorganisms. 8 (4), 575 (2020).</li><li>Liu, X. L., Raza, W., Ma, J. H., Huang, Q. W., Shen, Q. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dual+role+amino+acid+from+sesbania+rostrata+seed+exudates+in+the+chemotaxis+response+of+Azorhizobium+caulinodans+ORS571.">A dual role amino acid from sesbania rostrata seed exudates in the chemotaxis response of Azorhizobium caulinodans ORS571.</a> Molecular Plant-Microbe Interactions. 32 (9), 1134-1147 (2019).</li><li>Ling, N., Raza, W., Ma, J. H., Huang, Q. W., Shen, Q. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Root-secreted+malic+acid+recruits+beneficial+soil+bacteria.">Root-secreted malic acid recruits beneficial soil bacteria.</a> Plant Physiology. 148 (3), 1547-1556 (2008).</li><li>Shen, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+chemotaxis+on+Slipchip.">Bacterial chemotaxis on Slipchip.</a> Lab on a Chip. 14 (16), 3074-3080 (2014).</li><li>Liu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacillus+pumilus+LZP02+promotes+rice+root+growth+by+improving+carbohydrate+metabolism+and+phenylpropanoid+biosynthesis.">Bacillus pumilus LZP02 promotes rice root growth by improving carbohydrate metabolism and phenylpropanoid biosynthesis.</a> Molecular Plant-Microbe Interactions. 33 (10), 1222-1231 (2020).</li><li>Goswami, M., Deka, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+a+novel+rhizobacteria+having+multiple+plant+growth+promoting+traits+and+antifungal+activity+against+certain+phytopathogens.">Isolation of a novel rhizobacteria having multiple plant growth promoting traits and antifungal activity against certain phytopathogens.</a> Microbiological Research. 240, 126516 (2020).</li><li>Kaiira, M., Chemining'Wa, G., Ayuke, F., Baguma, Y., Nganga, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Profiles+of+compounds+in+root+exudates+of+rice,+cymbopogon,+desmodium,+mucuna+and+maize.">Profiles of compounds in root exudates of rice, cymbopogon, desmodium, mucuna and maize.</a> Journal of Agricultural Sciences Belgrade. 64 (4), 399-412 (2019).</li><li>Shi, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+rice+root+exudates+and+strain+combination+on+biofilm+formation+of+Paenibacillus+polymyxa+and+Paenibacillus+macerans.">Effect of rice root exudates and strain combination on biofilm formation of Paenibacillus polymyxa and Paenibacillus macerans.</a> African Journal of Microbiology Research. 6 (13), 3343-3347 (2012).</li><li>Lee, H. W., Ghimire, S. R., Shin, D. H., Lee, I. J., Kim, K. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allelopathic+effect+of+the+root+exudates+of+K21,+a+potent+allelopathic+rice.">Allelopathic effect of the root exudates of K21, a potent allelopathic rice.</a> Weed Biology and Management. 8 (2), 85-90 (2008).</li><li>Belimov, A. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rhizobacteria+that+produce+auxins+and+contain+1-amino-cyclopropane-1-carboxylic+acid+deaminase+decrease+amino+acid+concentrations+in+the+rhizosphere+and+improve+growth+and+yield+of+well-watered+and+water-limited+potato+(Solanum+tuberosum).">Rhizobacteria that produce auxins and contain 1-amino-cyclopropane-1-carboxylic acid deaminase decrease amino acid concentrations in the rhizosphere and improve growth and yield of well-watered and water-limited potato (Solanum tuberosum).</a> Annals of Applied Biology. 167 (1), 11-25 (2015).</li><li>Ankati, S., Podile, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolites+in+the+root+exudates+of+groundnut+change+during+interaction+with+plant+growth+promoting+rhizobacteria+in+a+strain-specific+manner.">Metabolites in the root exudates of groundnut change during interaction with plant growth promoting rhizobacteria in a strain-specific manner.</a> Journal of Plant Physiology. 243, 153057 (2019).</li><li>Gordillo, F., Chavez, F., Jerez, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motility+and+chemotaxis+of+Pseudomonas+sp.+B4+towards+polychlorobiphenyls+and+chlorobenzoates.">Motility and chemotaxis of Pseudomonas sp. B4 towards polychlorobiphenyls and chlorobenzoates.</a> FEMS Microbiology Ecology. 60 (2), 322-328 (2007).</li><li>Bais, H. P., Weir, T. L., Perry, L. G., Gilroy, S., Vivanco, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+root+exudates+in+rhizosphere+interactions+with+plants+and+other+organisms.">The role of root exudates in rhizosphere interactions with plants and other organisms.</a> Annual Review of Plant Biology. 57, 233-266 (2006).</li><li>Badri, D. V., Vivanco, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+and+function+of+root+exudates.">Regulation and function of root exudates.</a> Plant Cell Environment. 32 (6), 666-681 (2009).</li><li>Badri, D. V., Weir, T. L., Lelie, D., Vivanco, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rhizosphere+chemical+dialogues:+plant-microbe+interactions.">Rhizosphere chemical dialogues: plant-microbe interactions.</a> Curr Opin Biotech. Current Opinion in Biotechnology. 20 (6), 642-650 (2009).</li><li>Kamilova, F., Kravchenko, L. V., Shaposhnikov, A. I., Makarova, N., Lugtenberg, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+the+tomato+pathogen+Fusarium+oxysporum+f.+sp.+radicis-lycopersici+and+of+the+biocontrol+bacterium+Pseudomonas+fluorescens+WCS365.">Effects of the tomato pathogen Fusarium oxysporum f. sp. radicis-lycopersici and of the biocontrol bacterium Pseudomonas fluorescens WCS365.</a> Molecular Plant-Microbe Interactions. 19 (10), 1121-1126 (2006).</li><li>Kamilova, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organic+acids,+sugars,+and+L-tryptophane+in+exudates+of+vegetables+growing+on+stonewool+and+their+effects+on+activities+of+rhizosphere+bacteria.">Organic acids, sugars, and L-tryptophane in exudates of vegetables growing on stonewool and their effects on activities of rhizosphere bacteria.</a> Molecular Plant-Microbe Interactions. 19 (3), 250-256 (2006).</li><li>Badri, D. V., Vivanco, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+and+function+of+root+exudates.">Regulation and function of root exudates.</a> Plant Cell Environment. 32 (6), 666-681 (2009).</li><li>Hao, W. Y., Ren, L. X., Ran, W., Shen, Q. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allelopathic+effects+of+root+exudates+from+watermelon+and+rice+plants+on+Fusarium+oxysporum+f.sp.+Niveum.">Allelopathic effects of root exudates from watermelon and rice plants on Fusarium oxysporum f.sp. Niveum.</a> Plant and Soil. 336 (1-2), 485-497 (2010).</li><li>Hao, Z. P., Wang, Q., Christie, P., Li, X. 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Increasing research indicates that plant-bacteria interactions mainly occur in the rhizosphere and are influenced by root exudates20,21,22,23,24. Plant root exudates include a diverse array of primary metabolites, including phenolic acids, organic acids and amino acids as well as more complex secondary compounds25,<sup class=...

Chemotaxis is important for colonization of plant growth-promoting rhizobacterial (PGPR) on roots and for understanding plant-microbe interactions1. A class of low molecular weight compounds (chemoattractants) in plant root exudates induce the chemotactic movement of PGPR to the rhizosphere2. Malic acid, citric acid, and other components in the root exudates stimulate chemotaxis of Bacillus strains3. For example, glucose, citric acid, and fumaric acid in maize root exudates recruit bacteria&#160;to the root surface4. D-galactose, which&#160;is derived from root exudates,induces the chemotaxis of Bacillus velezensis SQR95. Organic acids, including fumarate, malic acid, and succinate, influence chemotaxis and colonization of various PGPR in the Cajanus cajan - Zea mays intercropping system6. Oleanolic acid in rice root exudates, acts as a chemoattractant for the strain FP357. Other plant exudates (including histidine, arginine, and aspartate) can play a crucial role in the chemotactic response of bacteria8. Plant exudates function as a signal to direct the movement of bacteria, which is the first step during rhizosphere colonization. Plant colonization by PGPR is a process of enormous relevance, as PGPR are beneficial for the plant host.
Many methods have been used for analyzing bacterial chemotaxis. The swimming plate method is one of the methods described previously9. In this method, plates were made with a semisolid medium. A chemotactic buffer containing agar (1.0%, w/v) was added to the plate. The buffer is heated, and then mixed with the chemoattractant. Then, 8 &#181;L of bacteria suspension was added dropwise to the middle of the plate and the plate was placed in an incubator at 28 &#176;C. The plate was regularly observed and photographed. However, the experimental cycle of the swimming plate method was very long. In the capillary-like method10, a pipette tip serves as a chamber for holding 100 &#181;L of bacterial suspension. 1 mL syringe needle was used as a capillary. A syringe needle containing chemoattractants with different concentration gradients was inserted into the 100 &#181;L pipette tip. After incubation at room temperature for 3 h, the syringe needle was removed, the content was diluted and plated on the medium. The bacterial accumulation in the syringe was represented by colony-forming units (CFUs) in the plates. However, the experimental error within replicates for the capillary-like method was large. Another method used a microfluidic SlipChip device11. Briefly, bovine serum albumin (BSA) solution was injected into all channels and removed using a vacuum. The solutions containing different chemoattractants (1 mM concentration for qualitative detection only), bacterial cells suspended in phosphate-buffered saline and phosphate buffered saline buffer (negative control) were added to the top, middle, and bottom microwells, respectively. Incubation was then performed in a dark environment at room temperature for 30 min. The bacterial cells were then detected in the microwells. The microfluidic SlipChip device, however, was expensive. Therefore, each of the methods described above had advantages and disadvantages.
We established an improved chemotaxis assay for the rapid identification of rhizobacterial chemoattractants in root exudates using sterile glass slides without complicated steps. In this study, through multiple comparisons of experimental results, the method overcame multiple shortcomings of traditional bacterial chemotaxis methods. The method reduced the error of plate counting and shortened the experimental cycle. Therefore, if used to identify a chemoattractant substance, this new method can save 2-3 days and reduce the cost of experimental materials.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2,5-dihydroxybenzoic acid</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>490-79-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>CNW Technologies</td>
			<td>75-05-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium acetate</td>
			<td>CNW Technologies</td>
			<td>631-61-8</td>
			<td></td>
		</tr>
		<tr>
			<td>Caffeic acid</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>331-39-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Thermo Fisher Scientific</td>
			<td>Heraeus Fresco17</td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>77-92-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Clean bench</td>
			<td>Shanghai Boxun Industrial Co., Ltd.</td>
			<td>BJ-CD</td>
			<td></td>
		</tr>
		<tr>
			<td>Ferulic acid</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>1135-24-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Formic acid</td>
			<td>CNW Technologies</td>
			<td>64-18-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Fructose</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>57-48-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Galactose</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>59-23-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>56-40-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Grinding Mill</td>
			<td>Shanghai Jingxin Industrial Development 
			Co., Ltd.</td>
			<td>JXFSTPRP-24</td>
			<td></td>
		</tr>
		<tr>
			<td>Histidine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>71-00-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Internal standard: 2-Chloro-L-phenylalanine</td>
			<td>Shanghai Hengbai Biotech C.,Ltd.</td>
			<td>103616-89-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Leucine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>61-90-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Malic acid</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>6915-15-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Mannose</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>3458-28-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Mass Spectrometer</td>
			<td>Thermo Fisher Scientific</td>
			<td>Q Exactive Focus</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>CNW Technologies</td>
			<td>67-56-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Optical Microscope</td>
			<td>Olympus</td>
			<td>BX43</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenylalanine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>63-91-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Proline</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>147-85-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Scales</td>
			<td>Sartorius</td>
			<td>BSA124S-CW</td>
			<td></td>
		</tr>
		<tr>
			<td>Serine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>56-45-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Threonine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>72-19-5</td>
			<td></td>
		</tr>
		<tr>
			<td>UHPLC</td>
			<td>Agilent</td>
			<td>1290 UHPLC</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasound Instrument</td>
			<td>Shenzhen Leidebang Electronics 
			Co., Ltd.</td>
			<td>PS-60AL</td>
			<td></td>
		</tr>
		<tr>
			<td>Valine</td>
			<td>Beijing InnoChem Science &#38; Technology C.,Ltd.</td>
			<td>7004-03-7</td>
			<td></td>
		</tr>
	</tbody>
</table>

an improved chemotaxis assay for the rapid identification of rhizobacterial chemoattractants in root exudates

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward method to quickly identify the chemoattractants that could induce the chemotactic movement of rhizosphere growth-promoting bacteria on sterile glass slides via simple steps. Bacteria solution (OD600 = 0.5) and sterile chemoattractant aqueous solution were added dropwise on the glass slide at an interval of 1 cm. An inoculating loop was used to connect the chemoattractant aqueous solution to the bacterial solution. The slide was kept at room temperature for 20 min on the clean bench. Finally, the chemoattractant aqueous solution was collected for bacterial counting and microscopic observation. In this study, through multiple comparisons of experimental results, the method overcame multiple shortcomings of traditional bacterial chemotaxis methods. The method reduced the error of plate counting and shortened the experimental cycle. For the identification of chemoattractant substances, this new method can save 2-3 days compared to the traditional method. Additionally, this method allows any researcher to systematically complete a bacterial chemotaxis experiment within 1-2 days. The protocol can be considered a valuable resource for understanding plant-microbe interactions.

A total of 584 and 937 known metabolites were detected in the positive and negative ion indices, respectively. Previous studies have shown that chemoattractants are typically organic acids, amino acids, and carbohydrates17,18.
In this study, 16 kinds of chemoattractants from the LC-MS studies in the rice rhizosphere exudates were selected for subsequent experiments (Table 1). Using the swimming plate method, we screene...

Watch this Scientific Journal Video about An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates at JoVE.com

An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates

Here, we present an improved chemotaxis assay protocol. The goal of this protocol is to reduce the steps and costs of traditional bacterial chemotaxis methods and to serve as a valuable resource for understanding plant-microbe interactions.

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward ...

The paper reported identification of chemoattractant of rhizobacteria in root exudates using an improved chemotaxis assay. Chemotaxis implant root actuates is significant for root colonization for plant growth, promoting rhizobia bacteria and for providing the helpful factions of plant-microbe interactions. Many methods were used for analyzing bacterial chemotaxis.For instance, swimming plate method, Cappilary like method, microfluidic slipchip device. The experiment cycle of swimming plate method was long. The experimental error of Cappilary like method was launched, microfluidic slipchip device is expensive to experiment.We established a straightforward method to quickly identify the chemoattractant that could induce the chemotactic movement of rhizosphere growth-promoting bacteria using sterile glass slides without complicated steps. The method reduced the error of the plate counting and shortened the experiment cycle. In regard to identifying a chemoattractant substance, the new method could save 2-3 days and also reduce the cost of experimental materials.Randomly distribute rice seeds in the grows chamber culture arises for a week and add sterile water twice. Select the rice seedlings of similar size and plant in a 50 milliliter of Ms liquid medium. Incubate for 48 hours at 22 degrees Celsius and a septic conditions.Rice root exudates will be released into the Ms medium. Liquid Chromatography Mass Spectrometry Analysis was performed using UHPLC system. Prepare chemoattractant aqueous solution ensure it is sterile.Filter the chemoattractant solution with a 0.22 micrometer bacteria filter. The chemoattractant aqueous solution was the single substance obtained from the LCMS studies dissolved in water. Citrix acid solution was used as example.All actions must be performed by the side of the lamp. Mark the middle position of glass slide at an interval of 1 centimeter. Ensure that the glass slide is sterilized several times on the flame.At the 30 microliter chemoattractant solution on the left of the glass slide ensure that bacteria was cultured to the logarithmic stage. Add the 30 microliter bacteria solution on the right of the glass slide. Sterilize inoculating loop several times on the flame using the inoculating loop to connect the chemoattractant aqueous solution to the bacteria solution and keep it at a room temperature for 20 minutes on a clean bench.After 20 minutes disconnect the connecting line with filter paper. Ensure that the 1.5 milliliter centrifuged tube is sterile. Collect the chemoattractant aqueous solution on the left of the glass slide.Transfer the solution to the 1.5 milliliters sterile centrifuged tube. Add the appropriate volume of the cell front dye to the centrifuged tube. After 2 minutes, collect the missible liquids for bacteria counting and microscopic observation with a blood counting chamber.Determine the number of the viable microorganisms attracted using a following equation. A higher RCI indicates a strong reaction to the chemoattractant. The results indicated that citric acid and Caffeic acid have the highest chemotaxis indices.The new chemotaxis assay method results wrote that bacterial can concentration of Citric acid, Caffeic acid and Galactose experiments were significantly higher than that of the control group and positive control. Citric acid wrote the strongest chemotaxis. The experimental results were in agreement with results of traditional methods.This video protocol can be presented as a valuable resource for clarification of plant-microbe interactions.

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