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Front. Cell. Infect. Microbiol. | doi: 10.3389/fcimb.2018.00062

Quantification of Live Bacterial Sensing for Chemotaxis and Phagocytosis and of Macropinocytosis

Netra Pal Meena1 and  Alan Kimmel1*
  • 1National Institutes of Health (NIH), United States

Initial immunological defense mechanisms to pathogen invasion rely on innate pathways of chemotaxis and phagocytosis, original to ancient phagocytes. Although chemotaxis has been well studied in mammalian and model systems using purified chemoattractants in defined conditions, directed movement towards live bacteria has been more difficult to assess. Dictyostelium discoideum is a professional phagocyte that chemotaxes toward bacteria during growth-phase in a process to locate nutrient sources. Using Dictyostelium as a model, we have developed a system that is able to quantify chemotaxis to very high sensitivity. Here, Dictyostelium can detect various chemoattractants at concentrations <1 nM. Given this exceedingly sensitive signal response, Dictyostelium will migrate directionally towards live gram positive and gram negative bacteria, in a highly quantifiable manner, and dependent upon bacterially-secreted chemoattractants. Additionally, we have developed a real-time, quantitative assay for phagocytosis of live gram positive and gram negative bacteria. To extend the analyses of endocytic functions, we further modified the system to quantify cellular uptake via macropinocytosis of smaller (<100 kDa) molecules. These various approaches provide novel means to dissect potential for identification of novel chemoattractants and mechanistic factors that are essential for chemotaxis, phagocytosis, and/or macropinocytosis and for more detailed understanding in host-pathogen interactive defenses.

Keywords: cell migration, Bacillus, Pseudomonas, E. coli, Dextran, Folate, Pterin, cAMP, innate immunity, Dictyostelium

Received: 31 Oct 2017; Accepted: 13 Feb 2018.

Edited by:

Thierry Soldati, Université de Genève, Switzerland

Reviewed by:

Salvatore Bozzaro, Università degli Studi di Torino, Italy
Robert R. Kay, Medical Research Council, United Kingdom  

Copyright: © 2018 Meena and Kimmel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Alan Kimmel, National Institutes of Health (NIH), Bethesda, United States, alank@helix.nih.gov