Screening of Bacillus mojavensis biofilms and biosurfactants using laser ablation electrospray ionization mass spectroscopy.

Authors: Bacon, Charles; Hinton, Dorothy; Mitchell, Trevor

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2018
Publication Date: 5/5/2018
Citation: Bacon, C.W., Hinton, D.M., Mitchell, T.R. 2018. Screening of Bacillus mojavensis biofilms and biosurfactants using laser ablation electrospray ionization mass spectroscopy. Journal of Applied Microbiology. 10.1111/JAM.13905.
DOI: https://doi.org/10.1111/JAM.13905

Interpretive Summary: Bacteria and other organisms produce structural substances called biofilms that are important to the producing species allowing communication between cells, along with the initiation of several biochemical compounds that synchronize the cell into a unicellular and focus organism. These synchronized cell are then are coordinated to produce important ecological and biochemical features that develop these otherwise unicellular organisms into a functional entities for successful existence. During the process important antimicrobials can be produced preventing the growth of competing organisms. We used Laser ablation electrospray ionization (LAESI) mass spectrometry to measure biofilms and two antimicrobials surfactin and fengycin during culture of Bacillus mojavensis, a biocontrol bacterium, used to control the corn pathogens Fusarium verticillioides and its fumonisin mycotoxins. This instrument is a modern approach useful for measuring the in situ interactions of organisms. Thus, we used LAESI to measure biofilms produced by several stains of this bacterium, along with the two antimicrobial surfactin and fengycin. The results of this study documented for the first time the ability of this biocontrol bacterium to produce biofilms, as well as correlating this ability to produce the two fungicidal compounds, surfactins, and fengycins. However, the relationships of biofilm production to the synthesis of the two antimicrobials were not apparent, and the synthesis of biofilms varied among the strain of the bacterium used. The study indicated that biocontrol ability of this bacterium might have important regulatory control beyond that expressed by the fungicidal substances usually attributed to these two lipopeptides thus indicating further research directions along the line of defensive signaling.

Technical Abstract: An aggregate of microorganisms within a matrix consisting of a chemically complex polymeric compounds and is produced by the organism constitute a biofilm. Bacterial biofilms are important self-produced structures in which the housed bacteria exhibit properties that are substantially different from free-living cell. Ecologically important developmental phases of cells within biofilm have altered phenotypes such as motility, swarming, signaling processes, antibiotic resistance, or antibiotic production, and for hydrophobic nutrient utilization. The roles of biofilm building for endophytic bacteria are however, unknown for those species used for biocontrol agents. One bacterial endophyte, Bacillus mojavensis, produces fengycin and surfactin, two biosurfactants, in culture. This endophytic bacterium has shown strong antagonisms to the maize pathogen Fusarium verticillioides, which also is a producer of the fumonisin mycotoxins. Successful application of B. mojavensis depends on its ability to survive and, more importantly, to be functionally relevant within this matrix, if indeed it does produce a biofilm. Therefore, it is important to determine the ability of strains used for biocontrol purposes to produce biofilms, and identify any biocontrol components within biofilms. Laser ablation electrospray ionization (LAESI) MS technology is a modern method that allows the in situ molecular cell imaging of tissues, resulting in a noninvasive measurement, and chemical analyses. We investigated the interaction of the endophytic biocontrol bacterium by LAESI MS to determine biofilm production relative to biocontrol components that are the lipopeptides, fengycin, and surfactin. We determined that strains of this bacterium produced biofilms, and that there is an accumulation of surfactin and fengycin, suggesting the potential functional value and ecological relevance as a structure from which biocontrols emerge.