Motile, Agile, Hostile (Updated)

Motility Testing 

     This past week we conducted motility tests on our particular soil microbes in order to further describe their identity. Motility allows microbes to move towards desired environments. Some stimuli that induce motility in microbes may be light, chemicals, food, and oxygen. Motility can come in a variety of different ways. Microbes may use actin filaments from whiting the cytoplasm to form actin tails on the external surface of the organism to move (M. Goldberg, 2001). Also, flagella are a common form of motility structures that allow microorganisms to change directions and move in desired directions (Kearns, 2010). Microbes that have evolved to equip motility into their lifestyle use it in many advantageous ways. Not only is motility useful in moving towards a desired environment that presents food and light, but some studies have revealed that motility can increase overall fitness in microbes by allowing a source of escape from undesirable conditions, including phages in bacteria (Taylor and Buckling, 2013). However, some microbes may utilize being non-motile for a variety of different reasons.  Pseudomonas aeruginosa is one such microbe responsible for causing pneumonia. It is much more prevalent in patents with cystic fibrosis. Research has shown that nonmotile phenotypes of this bacteria seem to be harder to get rid of because they are more resistant to phagocytosis by immune cells and conserve more enemy than that of strains of motile pathogens (Mahenthiralingam et al., 1994). So cells that are non motile may conserve more energy to put into certain virulence factors that would make them more pathogenic.
     The motility test of choice that we employed was the soft agar test. Inoculated needles are used to sample bacteria from culture and are then inserted into a tube containing soft agar. The needle punctures the agar until right above the butt of the tube. The tubes are left to incubate for 72 hours and then microbial growth is observed. If a strain grows outwards farther than from the point of inoculation throughout the agar, then it is deemed motile. If growth is observed only at the points of inoculation, then the strain is deemed non-motile. Our motility tests seemed to be inconclusive. Bacteria growth was observed from E. coli, but even this strain did not show motile growth that is has previously been identified with. Both our soil microbe and B. megaterium did not produce the desired microbial growth. We will conduct our motility tests again and update our findings. Once we confirm whether our soil microbe is motile or non-motile, we will then continue to further determine the true identity of our sample strain.

Update (4-12-15)

     The soft agar tests were ran again for the unknown soil microbe. Our results showed that the soil microbe is non-motile. Microbial growth did not disperse in medium from the inoculation point, so this implicates the bacteria does not have motility. From this information we may hypothesize that Corynebacterium is the genus that our microbe is categorized under. For instance, like the genus corynebacterium, our soil microbe is catalase negative, non-acid fast, and non-motile. Another possible genus could be lactobacillus, but this is less likely because lactobacillus are anaerobic microbes.

Goldberg, M. B. (2001). Actin-based motility of intracellular microbial pathogens. Microbiology and molecular biology reviews : MMBR, 65(4), 595-626, table of contents.

Kearns, D. B. (2010). A field guide to bacterial swarming motility. Nature reviews. Microbiology, 8(9), 634-644.

Mahenthiralingam, E., Campbell, M. E., & Speert, D. P. (1994). Nonmotility and phagocytic resistance of Pseudomonas   aeruginosa isolates from chronically colonized patients with cystic fibrosis. Infection and Immunity, 62(2), 596-605.

Taylor, T. B. and Buckling, A. (2013), Bacterial motility confers fitness advantage in the presence of phages. Journal of Evolutionary Biology, 26:   2154–2160. doi: 10.1111/jeb.12214