Catabolite repression

Catabolite repression helps the microorganism for faster adaptation within energy sources and abundance of carbon. This mechanism is achieved by enzyme synthesis that involves carbon source catabolism. In simpler terms, Catabolite repression refers to metabolite control exertion on the synthesis rate of specific enzymes.  

Many studies describe it as reversible procedures during the rapid catabolism process. It involves sensory and regulatory mechanisms in which protein, subunit targeting, and gene regulators are central. 

What is catabolite repression?  

With the initiation of catabolite repression, there is an uptake of catabolism of poor substrates. They are inhibited collectively through inducer exclusion. The process further follows global gene regulators who directly control gene transcription within the catabolism of carbon and energy production phases.  

It also includes gene regulators that indirectly control cell motility, carbons storage, changes in the cell surface, and cell division. The process of catabolite repression helps the bacteria increase their capabilities of being fit through growth optimisation. This is done by providing a complex nutrient mixture within the natural environment. 

Catabolite repression definition indicates that in most bacteria, the signal generation is done through enzymes that transport sugar and contribute to phosphorylation. This further leads to varied types of transduction mechanisms within catabolite repression.

Although, the actual regulation mechanism is different in varied types of bacteria. Hence, a carbon selection source is done at different carbohydrate levels. Therefore, it becomes important for controlling activity to keep the bacteria silent, even if genes can be controlled through controlling proteins. 

Regulating and controlling Bacteria metabolism 

The enzyme induction has been considered a negative control as it affects the active repressor of the molecule, which reduces the transcription rate. On the other hand, catabolite repression refers to positive transcription control, as protein in regulatory effects upregulates within transcription rate.

 The process of catabolite repression was propounded within E. coli and was referred to as the glucose effect. Many studies observed that glucose repression is the outcome of enzyme synthesis even if pathway inducers existed within the environment. 

A diauxic growth curve was introduced during the study that showcased two active phases. In the first phase, glucose was consumed until exhaustion, while in the second phase, lactose utilisation took place. The glucose availability kerbs lactose utilisation which is known as the glucose effect. 

Glucose was observed to act as an efficient repressor for inducible enzymes in varied types of bacteria. Studies also reveal that catabolite repression plays a vital role in expressing virulence-specific functions within several types of pathogens. The regulatory proteins within Catabolite repression have yielded good insights on antimicrobial chemotherapy functions. 

Many experiments on catabolite repression have focused on regulating proteins, while some considered glucose an alternative carbon source for limiting microbial growth. 

Catabolite repression and example

Catabolite repression and examples can be explained through a study or experiment to understand the glucose effect. The discovery for glucose effect was made in E.coli while regulating lac operon. In the first phase of bacteria growth, it was observed that glucose was utilised to the fullest as it was the only source of energy. 

Until glucose availability is diminished, the bacteria consume it to the fullest. In the secondary lag phase, lactose was consumed as no other energy was available to achieve exponential growth by the bacteria. 

The bacteria are provided different nutrients for growth instead of carbon. It is observed that when glucose is available in abundance, lactose utilisation is negligible because cells are not capable of transferring disaccharide lactose. 

Even if other sugars are present, glucose will also be consumed during the first phase of growth. Thus, the lactose operon will be repressed even if the inducer exists in the environment. The secondary lag period is the diauxic growth curve, representing the time required to complete lac operon induction and enzyme synthesis.

 After glucose is exhausted only then bacterial growth occurs on lactose. Since the abundance of glucose suppresses enzymes for utilising lactose, the repression is called catabolite or glucose effect. 

Catabolite repression within E.coli is modelled in mathematical calculations. This reveals that factors like protein are important participants in this type of repression. Although, global and operon-specific modelling for catabolite repression differ with genes. 

The glucose effect is considered to work effectively within the bacteria. Since cells are required to use the best alternatives of energy, in many bacteria, glucose is common and can be readily used for growth substrate. 

Conclusion 

Catabolite repressions are positive controls by providing an alternative source of energy. It is metabolism control on synthesis rate of particular enzymes. Catabolite repression works differently in varied genes of bacteria. The concept explains that apart from carbon, the bacteria only grow if provided with a different energy source. The bacteria will use the best source even if several sugar sources are available. As per the example, at every exponential growth phase, bacteria use one good energy source and repress the other.