Isolation and Characterization of Poly-gamma-glutamic Acid Producing Bacteria from Plant Rhizoplane

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Sirirat Siripornvisal*
Teerayuth Suddee


The purpose of this study was to isolate and evaluate the diversity of gif.latex?\gamma-PGA producing bacteria from rhizoplane of three Poaceae plants viz. rice (Oryza sativa Linn.), maize (Zea mays Linn.) and sugarcane (Saccharum officinarum Linn.), which are considered the most important agronomic crops of Thailand. A total of 368 isolates of rhizoplane bacteria were obtained from the root samples, 200 isolates from rice roots, 112 isolates from maize roots and 56 isolates from sugarcane roots. All isolates were screened for gif.latex?\gamma-PGA production consecutively by plate and tube culture assay. There were 186 isolates which exhibited gif.latex?\gamma-PGA producing capability. The gif.latex?\gamma-PGA concentrations obtained ranged from 12.62 - 18.46 g/L. Of those 186 isolates, 16 isolates were capable of producing gif.latex?\gamma-PGA higher than 15 g/l and these isolates were selected as the most efficient gif.latex?\gamma-PGA producers for further molecular characterization. The molecular genetic study based on 16S rRNA genes analysis revealed that the selected gif.latex?\gamma-PGA producers were closely related to 9 Bacillus species, namely B. amyloliquefaciens subsp. amyloliquefaciens, B. atrophaeus, B. methylotrophicus, B. siamensis, B. subtilis subsp. inaquosorum, B. subtilis subsp. subtilis, B. tequilensis, B. vallismortis and B. velesensis. All of them are belonging to B. subtilis and B. amyloliquefaciens groups. These results indicate that the rhizoplane of Poaceae plants are an important reservoir of natural isolates of gif.latex?\gamma-PGA producing bacteria.


Keywords: poly-gif.latex?\gamma-glutamic acid; gif.latex?\gamma-PGA; rhizoplane; Poaceae plants; Bacillus

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Ashiuchi, M. and Misono, H., 2002. Biochemistry and molecular genetics of poly-γ-glutamate synthesis. Applied Microbiology and Biotechnology, 59, 9-14.

Peng, Y., Jiang, B., Zhang, T., Mu, W., Miao, M. and Hua, Y., 2015. High-level production of poly (γ-glutamic acid) by a newly isolated glutamate-independent strain, Bacillus methylotrophicus. Process Biochemistry, 50, 329-335.

Tang, D.W., Yu, S.H., Ho, Y.C., Huang, B.Q., Tsai, G.J., Hsieh H.Y., Sung, H.W. and Mi, F.L., 2013. Characterization of tea catechins-loaded nanoparticles prepared from chitosan and an edible polypeptide. Food Hydrocolloids, 30(1), 33-41.

Liang, H.F., Chen, C.T, Chen, S.C., Kulkarni, A.R., Chiu, Y.L., Chen, M.C. and Sung, H.W., 2006. Paclitaxel-loaded poly (γ-glutamic acid)-poly(lactide) nanoparticles as a targeted drug delivery system for the treatment of liver cancer. Biomaterials, 27, 2051-2059.

Li, C., 2002. Poly (l-glutamic acid)-anticancer drug conjugates. Advanced Drug Delivery Reviews, 54, 695-713.

Tanimoto, H., Fox, T., Eagles, J., Satoh, H., Nozawa, H., Okiyama, A., Morinaga, Y. and Fairweather-Tait, S., 2007. Acute effect of poly-γ-glutamic acid on calcium absorption in post-menopausal women. Journal of the American College of Nutrition, 26, 645-649.

Yang, L.C., Wu, J.B., Ho, G.H., Yang, S.C., Huang, Y.P. and Lin, W.C., 2008. Effects of poly-γ-glutamic acid on calcium absorption in rats. Bioscience, Biotechnology and Biochemistry, 72, 3084-3090.

Shih, I.L., Van, Y.T. and Sau, Y.Y., 2003. Antifreeze activities of poly (gamma-glutamic acid) produced by Bacillus licheniformis. Biotechnology Letters, 25, 1709-1712.

Bhat, A.R., Irorere, V.U., Bartlett, T., Hill, D., Kedia G., Morris M.R., Charalampopoulos, D. and Radecka, I., 2013. Bacillus subtilis natto: a non-toxic source of poly-γ-glutamic acid that could be used as a cryoprotectant for probiotic bacteria. AMB Express, 3(1), 36. doi:10.1186/2191-0855-3-36

Lee, C.Y. and Kuo, M.I., 2011. Effect of γ-polyglutamate on the rheological properties and microstructure of tofu. Food Hydrocolloids, 25, 1034-1040.

Wang, F., Zhao J., Wei, X., Huo, F., Li, W., Hu, Q. and Liu, H., 2014. Adsorption of rare earths (III) by calcium alginate-poly glutamic acid hybrid gels. Journal of Chemical Technology and Biotechnology, 89, 969-977.

Zheng. H., Gao, Z., Yin, J., Tang, X., Ji, X. and Huang, H., 2012. Harvesting of microalgae by flocculation with poly (γ-glutamic acid). Bioresource Technology, 112, 212-220.

Shih, I.L. and Van Y.T., 2001. The production of poly-γ-glutamic acid from microorganisms and its various applications. Bioresource Technology, 79, 207-225.

Buescher, J.M. and Margaritas, A., 2007. Microbial biosynthesis of polyglutamic acid biopolymer and applications in the biopharmaceutical, biomedical and food industries. Critical Review in Biotechnology, 27, 1-19.

Zhang, H., Zhu, J., Zhu, X., Cai, J., Zhang, A., Hong, Y., Huang, J., Huang, L. and Xu, Z., 2012. High-level exogenous glutamic acid-independent production of poly-(gamma-glutamic acid) with organic acid addition in a new isolated Bacillus subtilis C10. Bioresource Technology, 116, 241-246.

Cao, M., Geng, W., Liu, L., Song, C., Xie, H., Guo, W., Jin, Y. and Wang, S., 2011. Glutamic acid independent production of poly-γ-glutamic acid by Bacillus amyloliquefaciens LL3 and cloning of pgs BCA genes. Bioresource Technology, 102, 4251-4257.

Ko, Y.H. and Gross, R.A., 1997. Effects of glucose and glycerol on γ-poly (glutamic acid) formation by Bacillus licheniformis ATCC 9945. Biotechnology and Bioengineering, 57, 430-437.

Ueda, Y., Frindte, K., Knief, C., Ashrafuzzaman, M. and Frei, M., 2016. Effects of elevated tropospheric ozone concentration on the bacterial community in the phyllosphere and rhizoplane of rice. PLoS One 11, e0163178.

Zeng, W., Lin, Y., Qi, Z., He, Y., Wang, D., Chen, G. and Liang, Z., 2013. An integrated high-throughput strategy for rapid screening of poly (gamma-glutamic acid) -producing bacteria. Applied Microbiology and Biotechnology, 97, 2163-2172.

Marchesi, J.R., Sato, T., Weightman, A.J., Martin, T.A., Fry, J.C., Hiom, S.J., Dymock, D. and Wade, W.G., 1998. Design and evaluation of useful bacterium-specific PCR primers that amplify genes coding for bacterial 16S rRNA. Applied and Environmental Microbiology, 64, 795-799.

Hall, T.A., 1999. BioEdit: a user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symposium Series, 41, 95-98.

Liu, J., He, D., Li, X-Z., Gao, S., Wu, H., Liu, W., Gao, X. and Zhou, T., 2010. γ-Polyglutamic acid (γ-PGA) produced by Bacillus amyloliquefaciens C06 promoting its colonization on fruit surface. International Journal of Food Microbiology, 142, 190-197.

Yu, Y., Yan, F., Chen, Y., Jin, C., Guo, J.-H. and Chai, Y., 2016. Poly-γ-Glutamic acids contribute to biofilm formation and plant root colonization in selected environmental isolates of Bacillus subtilis. Frontiers in Microbiology, 7, 1811. doi: 10.3389/fmicb.2016.01811