Introduction VIRUS Biofilms,


■ The study of biology is a point of Convergence for the information and tools from all the natural science. Biological system are the most complex Chemical systems on Earth, and their many functions are both determined and constrained by the principle of chemistry and physics. 

■ In its broadest sense Biology is the study of living things __ the science of life. Living thing come in an astounding  variety of shapes and forms.


■ Virus means venom or poisonous fluid. They are inert outside their specific host cell. Viruses are obligate parasites. 

■ virions: 

The main difference between virus and virion is that virus is the nucleoprotein particle whereas Virion is the active infectious form of the virus.

General Structure of the Viruses 

A fully assembled infectious virus is called a Virion.The simplest Virions consist of two basic  components. 
■ Nucleic acid ( single _ or double _ stranded RNA or DNA).

■ A protein coat, the Capside, which functions as a shell to protect the viral genome from nucleases during infection; it attaches the Virion to specific receptors exposed on the prospective host cell.

☆ Some virus families have an additional covering called the envelop, which is usually derived in part from modified host cell membranes.

☆ Viral envelopes consist of a lipid bilayer that closely surrounds a shell of virus _ encode membrane associated proteins. 

☆ The exterior of the bilayer is studed with virus _ coded, glgcosylated ( trans.) membrane proteins. Therefore , envoped viruses often exhibit a fringe of glycoprotein spikes or knobs.

☆ Viruses Cause diseases like mumps, smallpox,  herpes and influenza. 

☆ Adeno viruses are common viruses that cause a range of illnesses. They can cause cold like symptoms, feversore throat bronchitis,  pneumonia, diarrhea, and pink eye ( conjunctivitis).

■ Retroviruses:

A type of virus that has RNA instead of DNA as its genetic material. It uses an enzyme called reverse transcriptase to become part of the host cells DNA 

☆For example,  Covid _ 19 virus  

What is a positive sense and negative sense RNA virus? 

■ Positive Sense RNA virus is a type of single _ stranded RNA virus whose genetic material is viral MEAN that encodes for proteins. 

■ Postive _ sense

Single _ stranded RNA virus.

● In the host cell, the positive _ sense RNA of the virus is directly translated into viral  proteins. 

● It is 5' _ to _ 3' as the host mRNA 

● Since the host ribosome moves from 5' to 3 ' for translation the positive _ sense single _ stranded RNA is directly used for protein in synthesis. 

■ Negative _ Sense RNA virus refers to a type of single 

● These viruses contain negative _ sense RNA as genetic material. 
● It is not readable by the host ribosome. 
● First, the negative _ sense RNA ( 3' _ to_ 5') is converted into positive _ sense RNA (5'_ to_3') by viruses RNA _ dependent RNA Polymeras.

● The positive _ Sense RNA then functions as mRNA and is translated  into proteins in by the ribosome.

● This means they contain the sense strand of RNA as their genome and it can be readily translated into proteins. 

Negative Sense RNA Virus refers to a type of single 

Stranded RNA virus whose genetic material is the antisense strand of the viral mRNA. Hence, the negative strand RNA viruses consist of a genome that is complementary to the viral mRNA.

■ Therefore the viral genome cannot be readily translated into viral proteins. 

■ Prions :

 They are the misfolded proteins capable of producing many harmful pathogenic diseases. Prison Proteins that are found most abundantly in the brain.

■ Vioroid are infectious agents that consist only naked RNA without any Protection layer such as a Protein Coat.

■ Viroid infect plants ( but no other forms of life) and are replicated at the expense of the host cell.

■ Viroid genomes are small Single _ stranded Circles of RNA that are only 250  _ 400 baseslong.

● Lichens: 

Lichens are symbiotic associations i.e.matually useful associations between algae and fungi .

● The algal component is known as phycobiont and fungal component as mycobiont, which are Autotrophic and heterotropic,  respectively 

● Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for it partner.

● lichens are very good pollution indicators _ they do not grow in polluted areas. 

Cutturing Microorganisms in laboratory:

A microbiological culture also known as a microbial culture, is a process of growing microbial organisms in a predefined culture media under controlled laboratory circumstance. 

■ In culture microbes are grown on artificial growth medium. 

■ The artificial culture medium also known as the growth medium is an environment used for the growth of different types of microorganisms. 
■ The culture medium contains agarose and nutrients required the growth of the micro organism.
■ The medium is first sterilized so that there is no contamination in it, i.e, there is no growth of unwanted microbes and contains only the microbes of interest. 

● Microbes like Fungi and Bacteria can be cultured in artificial mediums.

■ Media most used for bacteria are nutrient agar. Media most used for fungi are potato dextrose agar and Sabouraud dextrose agar.

■ Special case of viruses 

☆ Viruses are obligate intracellular parasites that require living cells to replicate.

☆ Viruses lack metabolic machinery of their own and are dependent on their host cell for replication , they cannot be growth in synthetic culture media.

☆ Infect host cell ( eukaryotic or prokaryotic) can be cultured and growth and then the growth medium can be harvested as a source of virus.

■ Biofilms: An Emergent form of Bacterial life

■ Bacteria are able to grow adhered to almost every surface, forming architecturally Complex Communities termed Biofilms. 

■ In biofilm cell growth in multicellular aggregates that are encased in an  extracellular matrix produced by the bacteria themselves. 

■ Biofilms impact humans in many ways as they can form in natural, medical and industrial setting. For instance formation of biofilms an medical devices, such as Catheters or implants often results in difficult _ to _ treat  chronic infection.

Biofilm formstion.


■Moreover, inflections have been associated with biofilm formation on human surfaces such as teeth, skin, and the urinary tract.

■ However, Biofilms on human surfaces are not always detrimental. For example dental plaque Biofilms.

■ There are numerous benefits that bacteria community might obtain from the formation of Biofilms. 

☆ Biofilms Confer resistance to many antimicrobials, protection from Protozoan grazing and protection against host defenses.

■ The molecular mechanisms that regulate Biofilm formation vary greatly among different species, and even vary between different strains of the same species.

  ■ However some features are recognized as general attributes of biofilm formation instance, all biofilms contain extracellular matrix that hold cells together.

 ■ This matrix is often composed of a Polysaccharide bio polymer along with other components such as proteins or DNA.

■ The nature of the matrix exopolyscxaride greatly varies depending on growth conditions, medium.

Write down the differences between Prokaryotic and Eukaryotic cell.? 

Ans : Cell is the fundamental and functional unit of life. Based on Complxity of structure, cell can be classified into Eukaryotic cell and Prokaryotic 

Prokaryotic cell:

1: The Prokaryotes lack nuclei and other membrane bound organelles. 

2: They consist of cytoplasm surround by a plasma membrane and are encased within a rigid cell wall.

3: Prokaryotes are very important in the ecology of living Organisms. Some harvest light by Photosynthesis,  other breakdown dead organisms and recycle their components. 

4: Example: Cyanobacteria, thermophiles helophiles,etc.

Eukaryotic cells

1: All eukaryotes ( having " true nucleus" ) have cells with a membrane _ band nucleus containing  DNA.

2: In addition,  Eukaryotic cells contain many other structures called organelles (" little organs") that perform specific functions. 

3: Eukaryotic cells also have a network of specialized structure called micro _ filaments and microtubules organized into the cytoskeleton which givesshope to the cell and allows intracellular movement. 

4: Example plants, animals,  fungi, etc.

In environment life is dependent on the recycling of elements. Prokaryotes and Eukaryotes form a Symbiotic relationship in which Prokaryotes help in decomposition of chemical compounds while Eukaryotes help in nitrogen fixation. 

It is important to protect and take care of every ,species as the food cycle and food web is the basis of life on Earth. 


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