Question

Please answer the following questions regarding your microbe. Please cite all of your sources.

a) What is the life cycle of disease for your microbe in humans?

b) What virulence factors does your microbe possess?

c) What is known about the regulation and function of the virulence factors in your microbe?

Answer 1

a) The life cycle of microbe consist of Lag phase, Log phase ,Stationary phase and Death phase.

Microbes does not grow during Lag phase. They adjust with the environment metabolise to produce vitamins and amino acids for deletion. They starts making copy of their DNA and is the environment supplies plenty of nutrients , the Lag phase may be very short. Then it will proceed to the next phase of their life.

Log phase is also known as exponential phase. During this phase microbes multiply rapidly, even exponentially. The time it take for a culture to double is called generation time and under the best condition, the fastest microbes can double in about 15 minutes. Within a bacterium the DNA copy drift to the opposite side of the membrane. The bacterium then pulls apart creating two identical daughter cells which being dividing a new. This process is called binary fission.

During stationary phase due to accumulating waste and lack of space microbes can not maintain the clip of log phase. If the microbes move to another culture, rapid growth may resume.

During Death phase Bacteria losses its ability to reproduce which become their death knell . Like Log phase bacterial death may occur as rapidly as their growth.

b) Virulent Factors

• Enzymes:

Enzymes that are considered as virulence factors are generally active against host components and contribute to virulence by damaging host tissue. Tissue damage makes the host permissive for host microbial infection. Enzyme virulent factors that damage tissues include proteases , neurominidases and phospholipases. These enzyme damage cells and provide nutrients by digesting substrates into smaller components that can be assimilated by microbes.

• Motility  

Motility is a complex trait that has been associated with virulence in both Bacteria and Parasite. Motility is manifested by approximately 80% of known-bacterial species and is critical for the adaptation of mobile microbes to new environment. Bacterial cells can move by the action of specialized organells called Flagella. Actin based motility is used by several intra cellular pathogens.

• Capsules

Many pathogenic bacteria posses poly saccharide capsules which are required for virulence in mammalian host. Most capsule function in microbial pathogenesis by protecting the microbes against host immune mechanism although for some of the capsular structure can serve as adhesins.

• Adhesins

Adhesins are microbial components that enable a microbe to attach to host tissue. Since it is widely accepted that attachment is required for most microbes to infect and grow in a host , adhesins are considered as virulent factors. Adhesins are chemically diverse molecules that includes proteins , poly saccharides, and bacterial cell wall components

c) Regulation of virulence factors through identification and analysis to better understand the infectious process in hopes that new diagnostic techniques, specific antimicrobial compounds , and effective vaccines or toxoids may be eventually produced to treat and prevent infections. There are 3 general experimental ways for the virulence factors to be identified: biochemically, immunologically , and genetically. For the most part, a genetic approach is the most extensive way in identifiying the bacterial virulence factors . Bacterial DNA can be altered from pathogenic to non pathogenic, random mutations may be introduced to their genome, specific genes encoding for membrane or secretory products may be identified and mutated, and genes that regulate virulence genes may be identified.

Virulence factors produced by individual pathogens which determine the extend and severity of disease they may cause.

The pathogen's virulence factors are encoded by genes that can be identified using molecular Koch's postulates. When genes encoding virulance factors ere inactivated, virulence in the pathogens is diminished.