Microbial cells analysis by atomic force microscopy

In Situ Imaging of Candida albicans Hyphal Growth via Atomic Force Microscopy

Candida albicans is one of the most common pathogens of humans. One important virulence factor of C. albicans is its ability to form elongated hyphae that can invade host tissues and cause disseminated infections. Here, we show the effect of different physiologically relevant temperatures and common antifungal drugs on the growth and mechanical properties of C. albicans hyphae using atomic force microscopy. We demonstrate that minor temperature fluctuations within the normal range can have profound effects on hyphal cell growth and that different antifungal drugs impact hyphal cell stiffness and adhesion in different ways.

Candida albicans is an opportunistic fungal pathogen of humans known for its ability to cause a wide range of infections. One major virulence factor of C. albicans is its ability to form hyphae that can invade host tissues and cause disseminated infections. Here, we introduce a method based on atomic force microscopy to investigate C. albicans hyphae in situ on silicone elastomer substrates, focusing on the effects of temperature and antifungal drugs. Hyphal growth rates differ significantly for measurements performed at different physiologically relevant temperatures. Furthermore, it is found that fluconazole is more effective than caspofungin in suppressing hyphal growth. We also investigate the effects of antifungal drugs on the mechanical properties of hyphal cells. An increase in Young’s modulus and a decrease in adhesion force are observed in hyphal cells subjected to caspofungin treatment. Young’s moduli are not significantly affected following treatment with fluconazole; the adhesion force, however, increases. Overall, our results provide a direct means of observing the effects of environmental factors and antifungal drugs on C. albicans hyphal growth and mechanics with high spatial resolution.

IMPORTANCECandida albicans is one of the most common pathogens of humans. One important virulence factor of C. albicans is its ability to form elongated hyphae that can invade host tissues and cause disseminated infections. Here, we show the effect of different physiologically relevant temperatures and common antifungal drugs on the growth and mechanical properties of C. albicans hyphae using atomic force microscopy. We demonstrate that minor temperature fluctuations within the normal range can have profound effects on hyphal cell growth and that different antifungal drugs impact hyphal cell stiffness and adhesion in different ways.

Basic concepts and physical-chemical phenomena, that have conceptual meaning for the formation of systemic clinical thinking and formalization of the knowledge of systemic structural-functional organization of the human’s organism

From the point of view of perception and generalization processes there are complex, logic and conceptual forms of thinking. Its conceptual form is the highest result of interaction between thinking and speech. While realizing it, human uses the concept, which are logically formed thoughts, that are the meaning of representation in thinking of unity of meaningful features, relations of subjects or phenomena of objective reality. Special concepts, that are used in the science and technique are called terms. They perform a function of corresponding, special, precise marking of subjects and phenomena, their features and interactions. Scientific knowledge are in that way an objective representation of material duality in our consciousness. Certain complex of terms forms a terminological system, that lies in the basis of corresponding sphere of scientific knowledge and conditions a corresponding form and way of thinking. Clinical thinking is a conceptual form, that manifests and represents by the specialized internal speech with gnostic motivation lying in its basis. Its structural elements are corresponding definitions, terms and concepts. Cardinal features of clinical systems are consistency, criticality, justification and substantiation. Principles of perception and main concepts are represented in the article along with short descriptions of physical and chemical phenomena, that have conceptual meaning for the formation of systematic clinical thinking and formalization of systemic structural-functional organization of the human’s organism

Mechanobiology of Antimicrobial Resistant Escherichia coli and Listeria innocua

A majority of antibiotic-resistant bacterial infections in the United States are associated with biofilms. Nanoscale biophysical measures are increasingly revealing that adhesive and viscoelastic properties of bacteria play essential roles across multiple stages of biofilm development. Atomic Force Microscopy (AFM) applied to strains with variation in antimicrobial resistance enables new opportunities for investigating the function of adhesive forces (stickiness) in biofilm formation. AFM force spectroscopy analysis of a field strain of Listeria innocua and the strain Escherichia coli K-12 MG1655 revealed differing adhesive forces between antimicrobial resistant and nonresistant strains. Significant increases in stickiness were found at the nanonewton level for strains of Listeria innocua and Escherichia coli in association with benzalkonium chloride and silver nanoparticle resistance respectively. This advancement in the usage of AFM provides for a fast and reliable avenue for analyzing antimicrobial resistant cells and the molecular dynamics of biofilm formation as a protective mechanism.