Bacterial Motility in Different Environments

Question: Discuss about the Bacterial Motility in Different Environments. Answer: Introduction The literature review is based on mobility of bacteria in different surroundings. Bacterial motility is executed by Motile Escherichia coli (E.coli). The ability of bacteria to move from one place to another by help of flagella is called bacterial motility (Hagai et al. 2014). This literature review focuses on environmental impact on bacterial motility, superiority of spatial sensing to temporal sensing, bacterial strategies of swimming, mechanism of gradient sensing and influence of scaling and energy. It also emphasizes on chemotactic reaction of aquatic microorganisms, extent to which growth and competition is influenced by the availability of nutrients, influence of organic nutrients and oxygen on migration of mobile E.coli and provision of bacterial dispersal on solid surface motility. According to a study on environmental impact on bacterial motility, the mobility of Escherichia coli was inhibited by heavy metal ions at low concentration. It was found that the motility rate could be enhanced by chelating of these metals stimulated by amino acids. Excellent motility rate of E.coli was found by replacing peptone (a complex medium for motility) by chelating agents, a source of energy and a buffering agent. It was observed that that flagella synthesis was prevented by glucose that imparts an inhibitory effect (Adler and Templeton 1967). According to a comparative study made on the superiority of spatial sensing to temporal sensing in bacterial motility, it was found that under certain habitat conditions the spatial sensing could function better as compared to temporal sensing mechanism. However, at low concentration range and shallow gradient, the temporal mechanisms are found to be more functional and advantageous in mobility of bacteria. Nevertheless, in case of spatial sensing where size is the limiting factor, it was observed that bacterial chemotaxis took place. Thus, it was concluded that temporal or spatial mechanism was favored depending on the specific environmental conditions (Dusenbery 1998). A study on bacterial strategies of swimming and conditions of turbulence suggests that the strategy of back and forth was superior to back and tumble strategy of swimming in terms of efficiency. It was previously studied that chemotaxis facilitates the bacteria in keeping close proximity with the food source despite of high shear stress. This strategic swimming mechanism can be enhanced further more in terms of efficiency by rotational diffusion by virtue of a driving force of thermal noise (Luchsinger, Bergersen and Mitchell 1999). According to a study on mechanism of gradient sensing in bacterial chemotaxis, it was found that gradients are detected by temporal sensing mechanism in bacteria. The study was conducted by developing a typical model of temporal apparatus. This model was subjected to abrupt modifications in concentration range of the attractants. The tumbling effect associated with spatial gradient was elicited with decrease in the concentration level. It was also observed that a sudden increase in concentration results in elicitation of a response called super coordinated swimming. Thus, it was demonstrated that below and above the stable state, chemotaxis could be achieved by modulating the turbulence (Macnab and Koshland 1972). A study on the influence of scaling and energy in bacterial motility demonstrated that bacterial size has an impact on its movement. It was studied by determining the cost of four bacterial strategies of chemotaxis in terms of energy expenditure. The study involved different sized bacteria. The results showed that the chemotactic strategies involved in bacteria have the similar functioning in context of size to energy expenditure as observed in animals. This adaptation is acquired by variation in the locomotory strategies depending on the bacterial size and surrounding (Mitchell 2002). According to a study on the chemotactic reaction of aquatic microorganisms towards nutrient sources, it was found that the oceanic thermodynamics and biogeochemical drift have strong connection with the resource exploitation by microbes. It was found that the swimming microorganisms face certain obstructions like turbulent shear and molecular diffusion. These factors limit the accessibility of nutrients as well as also affect its capability to find the nutrient source. Many theoretical predictions were made previously, but a practical approach of using microfluids led to better understanding of microbial behavior and marine ecology (Seymour and Marcos 2007). A study was conducted to investigate the extent to which growth and competition of the microbial colonies present in micropatches are influenced by the availability of nutrients. The sources of these nutrients were also studied. The chemotactic microorganisms (bacteria) were inspected for their swimming behaviour and pattern. It was observed that bacterial clusters by Protozoa were formed because of conjugation along with cell break down and elimination. The nutrient sources were spread inside the patches having diameter of a few millimeters. It was observed that for about 10 minutes the bacterial swarms were retained. During this period of retention, the bacteria were encountered by large amount of nutrients. Thus, it was concluded that chemotaxis was beneficial for the bacteria utilizing micropatches (Blackburn, Fenchel and Mitchell 1998). According to a study, organic nutrients along with oxygen influenced the migration of mobile E.coli in bands. The study was conducted by placing the mobile E.coli in a capillary tube consisting of nutrient and oxygen. It was observed that the contents migrated out of the tube followed by one or two band formation. It was found that the bacteria created a gradient of oxygen and nutrient source. They moved along the pathway that involved higher concentration of chemical agents. Thus, it was concluded that chemotaxis helps the bacteria to find favorable surroundings that provide optimal nutrient and oxygen supply (Adler 1966). A study stated bacterial dispersal on solid surface is promoted by surface motility in respect to their induction, attraction and hitchhiking. It was found that the bacteria get benefitted ecologically due to its locomotive capability on solid surface. Xanthomonas sp. has this advantageous trait because it utilizes motile bacteria present in the surroundings. X.perforans and Paenibacillus vortex were used as models for the study. It was observed that X.perforans promoted surface mobility and attracted mobile bacteria to drive them for dispersal (Hagai et al. 2014). Conclusion The review of literature has been done based on various aspects of bacterial motility under different environment. It is found that chelating agents to promote bacterial motility can replace glucose, spatial sensing is favoured under certain environmental conditions, and back and forth swimming strategy is preferred. It is also found that gradients are detected by temporal mechanism, bacterial motility is influenced by size, microfluids help in better understanding of microbial behaviour and microbial growth is influenced by food accessibility, bacterial migration is influenced by oxygen and bacterial dispersal on solid surface. Therefore, it is concluded that environment plays a great role in bacterial motility. References: Adler, J. and Templeton, B., 1967. The effect of environmental conditions on the motility of Escherichia coli.Microbiology,46(2), pp.175-184. Adler, J., 1966. Chemotaxis in bacteria.Science,153(3737). Blackburn, N., Fenchel, T. and Mitchell, J., 1998. Microscale nutrient patches in planktonic habitats shown by chemotactic bacteria.Science,282(5397). Dusenbery, D.B., 1998. Spatial sensing of stimulus gradients can be superior to temporal sensing for free-swimming bacteria.Biophysical journal,74(5), pp.2272-2277. Hagai, E., Dvora, R., Havkin-Blank, T., Zelinger, E., Porat, Z., Schulz, S. and Helman, Y., 2014. Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.The ISME journal,8(5). Luchsinger, R.H., Bergersen, B. and Mitchell, J.G., 1999. Bacterial swimming strategies and turbulence.Biophysical journal,77(5), pp.2377-2386. Macnab, R.M. and Koshland, D.E., 1972. The gradient-sensing mechanism in bacterial chemotaxis.Proceedings of the National Academy of Sciences,69(9), pp.2509-2512. Mitchell, J.G., 2002. The energetics and scaling of search strategies in bacteria.The American Naturalist,160(6), pp.727-740. Seymour, J.R. and Marcos, R.S., 2007. Chemotactic Response of Marine Micro-Organisms to Micro-Scale Nutrient Layers.Journal of visualized experiments: JoVE, (4). Tuson, H.H. and Weibel, D.B., 2013. Bacteriasurface interactions.Soft matter,9(17).