Sarah Manmiller (1 PM Micro) was interested in this report from Science Daily on how bacteria are able to regulate genes in response to environmental changes.
In order for scientists to develop new drugs and antibiotics to combat bacteria they need to better understand how bacterial cells work. A recent study done on the physiological responses of the bacteria called B. subtilis in stressful environments gave a new insight as to how bacterial cells regulate a homeostatic state. Prior to this study, bacterial responses were thought to turn particular genes on while in stressful environments and leave them on until the stressor disappeared. Now, a new cellular response utilizes a pulsating mechanism that is activated by genes while the bacteria are under stress. The bacteria are able to turn these genes on and off in times of hardship, contrary to belief.
One of the environments B. subtilis was placed in contained no food. The stress placed on the bacteria caused the bacteria to begin a pulsating action, which allowed the bacteria to turn to the genes on and off. Depending on the stressor and the intensity of the stress the pulsating action can increase or decrease. Another environment B. subtilis was placed in contained a chemical that impedes the production of ATP. This stimulus actually turned on specific interactions within the same set of genes. These interactions are grouped together in what is known as a genetic circuit. The circuit is made up of positive and negative feedback loops that creates activation pulses of a regulatory protein called sigma B. When fluorescent proteins are attached to the circuit, movies displayed the activation of sigma B by highlighting the cells green. The movies were able to show the gene circuit amplifying the increase of sigma B activations during times of stress, also known as noise. The circuit can be analogous to some homeostatic events that occur on a large scale in the human body, such as the regulation of temperature. The movies showed that the pulsating mechanism is the variability that effects how proteins are made. The pulsating mechanism could be seen as the contraction of muscles in the body to help raise the internal temperature of the body. The study also showed that the stress put onto the bacteria activated another key protein that regulates the pulse frequencies in the cell. The second protein that is activated assists in the production of sigma B.
The importance of the study however, was proof to how a minute genetic circuit can create complex and vast behaviors in a cells response to stimuli. This suggests that some cellular processes and homeostatic controls that were seen as complicated could be controlled by cellular responses that activate genes to increase the production of specific proteins. These proteins then have specific functions within the cell to help counter balance the environmental stimuli. The study gave new light to how cellular control actually works, which was not easily seen prior to the experiment. In the future this study may be expanded to see if the same genetic circuit or parts of it appear in other complex systems, including mammalian cells.