Atomic force microscopy has been an important tool in the study of atomic orientation, macromolecular structure, surface structure, morphological structure of living/nonliving tissues and synthesized materials. Although ten modes of imaging are routinely used, all information on surface structure and forces are obtained from the oscillation of the cantilever at its resonance frequency which is induced by the piezoelectric element. The photodetector senses deviations of the laser deflected off the surface of the cantilever from the norm resonance caused by attractive and repulsive forces between the tip of the cantilever and the sample. All oscillations and torsions of the cantilever that do not correspond to the sinusoidal wave produced can be converted to topographic images and force curves of the sample.

In reference to the project, AFM technology aids in the visualization of important physiochemical characteristics of lactic acid bacteria (LAB) including Lactobacillus acidophilus NCFM strains. LAB has important immunomodulatory effects that induce the gastrointestinal tract to homeostasis health. Single bacteria strains and combination of strains adhered to milk fat globule membranes (MFGM) introduced to gastrointestinal tract (GIT) via milk fat globules (MFG) have been found to prevent and reduce illness by providing improved mucosal immunity of the GIT. MFG allow adhered LAB increased probability of subsisting through bile, stomach acid and other autoimmune defenses. Central to this function is the composition and structure of the surface of these important microorganisms. We have some single gene deletion mutants of genes important for the outer surface of NCFM. DNA analysis also yields good quantification of observed binding dependent upon mutation type and expression of surface proteins. Therefore, it is crucial to study the morphology in LAB that contribute to adherence to MFGM. Using milk fat could be a means of supplying the world with probiotics that maintain a healthier lifestyle.


Derek Gragson and Rafael Jiménez-Florez

Lab site

California Polytechnic State University (Cal Poly SLO)



URL: https://digitalcommons.calpoly.edu/star/29


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