Not All Log Cells are Created Equal — 100p — Jared Volesky, Manisha Guha, Nicholas C. Butzin

Department of Biology and Microbiology; South Dakota State University; Brookings, SD,  57006; USA  

Isogenic bacterial cells in the log (exponential) growth phase are often described as  homogenous, uniform, and having identical phenotypes. If such is the case, then the length of  bacterial cells should be nearly identical (ranging from the size of a whole cell to that of a  dividing cell) throughout the log phase. However, we see many cells of different sizes in the log  phase. We also noticed that the average bacteria become larger in length the longer they are in  the log phase. Interestingly, the cells begin to shrink even before they enter the transition phase  (the progression from the log to the stationary phase). Cells enter the transition phase when  their micro-environment starts to become inhospitable or low in nutrients. This is a qualitative  observation, and there is no quantitative or statistical data we could find in the literature.  Accordingly, we have two hypotheses: (1) Cells increase their length in the log phase as they  adapt to a plentiful, favorable environment. (2) Cells sense in the mid-log phase that the  environment is changing, and in response, alter their cell length in the late-log phase but  maintain their growth rate over an hour before entering the transition phase. We can test these  hypotheses by cultivating Bacillus megaterium (a gram-positive bacterium) in liquid culture and  imaging thousands of cells over time at distinct time points. Using custom scripts, we can  measure the length of individual cells at each time point in the log, transition, and stationary  phases. If the length of the cells increases over time in liquid culture, we will overturn the long held established dogma that the majority of the cells are doing the same thing throughout the  log phase. 

South Dakota State University
Dr. Nicholas Butzin