Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Short CommunicationDifferentiation in MALDI-TOF MS and FTIR spectra between two pathovars of Xanthomonas oryzae
Graphical abstract
MALDI-TOF MS protein mass fingerprint of (a) Xanthomonas oryzae pv. oryzicola and (b) Xanthomonas oryzae pv. oryzae. Similar and different marker masses for the identification of (a) and (b) are listed in Table 2. Intensity of ions is shown on the Y axis and the mass (in Daltons) of the ions is shown on the X axis. The m/z values represent mass to charge ratios. The unique peaks positions are marked for each of species in Fig. 1.
Introduction
Two important rice pathogenic bacteria Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc) are closely related phenotypically and genetically. For example, the two pathovars were able to cause similar symptoms. Furthermore, there was a high level of phenotypical and genetic diversity among strains of each pathovar. These data suggested that the two pathovars were often not easy to be differentiated based on traditional phenotypic and DNA-based methods [1], [2], [3], [4]. Nowadays, many researches have focused on the development of an effective method for the differentiation of both pathovars of X. oryzae [1], [2], [3], [4], [5], [6]. Indeed, a new primer has been recently designed based on in-depth comparative genome analyses [7]. However, this still require time-consuming PCR procedures.
Fortunately, in recent years, MALDI-TOF MS and Fourier Transform Infrared (FTIR) spectra have been successfully applied in bacterial identification and classification [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. MALDI-TOF MS allows bacterial identification at the species level by measuring molecular masses of proteins and other components obtained from whole bacterial extracts, while FTIR spectroscopy allows the analysis of small quantities of biomass, simultaneous characterization of different functional groups such as lipids, proteins, nucleic acids and polysaccharides in biological molecules and complex structures and without disturbing the systems, and requires no consumables or reagents [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19]. However, little information was available about the applications of MALDI-TOF MS and FTIR spectra in the two rice pathogenic bacteria.
The purpose of this study is to develop a rapid and accurate approach to identify the two closely related pathovars of X. oryzae based on their MALDI-TOF MS and FTIR spectra.
Section snippets
Bacterial strains and culture conditions
The virulent strains of Xoo and Xoc used in this study were isolated from diseased rice leaves, while 10 strains among each species were selected for further analysis in this study (Table 1). The identities of bacterial strains were determined and confirmed based on the analysis of biochemical and physiological characteristics, the whole-cell fatty acid and Biolog carbon utilization as well as 16S rRNA gene sequence [20], [21], [22], [23].
MALDI-TOF MS
Bacterial strains were growed on sucrose peptone agar
Bacterial identity
In this study, the Xoo strains were identified as X. oryzae pv. oryzae with Biolog similarity of 0.71–0.80, FAME similarity of 0.75–0.81, and 16S rRNA sequence similarity of 99%, while the Xoc strains were identified as X. oryzae pv. oryzicola with Biolog similarity of 0.75–0.83, FAME similarity of 0.71–0.85, and 16S rRNA sequence similarity of 99%. However, there was a high similarity in the profile of Biolog and FAME as well as 16S rRNA sequence between the Xoo and Xoc strains, which make
Conclusion
Overall, our results indicated that there was a significant difference in MALDI-TOF MS and FTIR spectra between the two pathovars. In particular, several specific characteristic peaks were determined for each of the two pathovars. Compared to the traditional time-consuming methods, both of the two methods are easy and rapid for comparison of the two pathovars of X. oryzae. Indeed, MALDI-TOF MS is a new proteomics-based strategy, while FTIR spectroscopy is a physic-chemical technique in
Acknowledgements
This work was supported by National Natural Science Foundation of China (31371904), Zhejiang Provincial Natural Science Foundation of China (R13C140001; Y3090150), Zhejiang Provincial Project (2014C32010; 2010R10091), the Fundamental Research Funds for the Central Universities, the Agricultural Ministry of China (nyhyzx 201303015; 201003029; 201003066), the Zhejiang Open Foundation of the Most Important Subjects (KF201328) and Key Subject Construction Program of Zhejiang for Modern Agricultural
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