Make the diagrams of any four types of microorganism write their role in brief.
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Answers
Answer:
Explanation:
The five major groups of microbes
Microbes are organisms that are too small to be seen with the unaided eye. As you’ll see later in the course, they evolved long before the first plants and animals appeared and affect our lives in more ways than we might expect.
Microbiologists are discovering new species of microbe at a faster rate than ever, thanks to advances in DNA sequencing techniques. Current estimates suggest there could be at least 1 billion different species of microbe on Earth, possibly more. Microbial diversity is truly staggering, yet all these microbes can be grouped into five major types: Viruses, Bacteria, Archaea, Fungi, and Protists.
Let’s look at each one in more detail.
Viruses
Viruses are the smallest of all the microbes. Their genome is made of either DNA or RNA (not both), and this is packaged inside a protein shell called a capsid. They are not made of cells (acellular), cannot make their own proteins and don’t grow. Instead, they must infect a host cell and hijack its machinery to assemble new viruses. Viruses are usually only able to infect a limited number of species living organism. Bacteriophages (Figure 1) are viruses that infect bacteria. In some countries they are used to treat bacterial infections and there is renewed interest in phage therapy due to the alarming increase in antimicrobial resistant infections.
2D: DNA, Protein. 3D: Head, Collar, Tail, Long tail fibres, Base plate
Figure 1: Structure of bacteriophage T2. The 2D diagram on the left shows the structure of the protein capsid (black) and the nucleic acid genome (blue) packaged inside the head that is attached (via the collar) to a hollow contractile tail. The 3D diagram on the right shows the head has an icosahedral structure and the long tail fibres extend from the base plate at the bottom © Adenosine (original); en:User:Pbroks13 (redraw) CC BY-SA 2.5
Some viruses have a lipid envelope which they steal from membranes in the host cell. An example of an enveloped virus that you will be familiar with from News articles (and likely will have experienced the effects of personally) is influenza virus (Figure 2) which causes influenza or the ‘flu’. The 1918-19 flu pandemic was the worst outbreak on record, infecting one third of the global population and killing around 50 million people.
This is a 3-dimensional illustration showing the different features of an influenza virus, including the surface proteins hemagglutinin (HA) and neuraminidase (NA)
Figure 2: Structure of influenza virus. The 8 segments of the RNA genome are packaged inside the virus particle, each piece of RNA is bound by protein that together form ribonucleoproteins (green). These are packaged inside the viral envelope (which the virus steals from the host cell membrane) that is embedded with viral proteins (light blue, red and dark blue) that play important roles in the virus replication cycle © CDC/ Douglas Jordan; Dr. Ruben Donis, Dr. James Stevens Dr. Jerry Tokars, Influenza Division
Whilst a few viruses can respond to changes in their environment, and you could argue that this is a form of sensitivity (the S in MRS GREN – see below), they aren’t capable of the majority of life processes. Most scientists agree that viruses should therefore be considered non-living.
In contrast to viruses, bacteria, archaea, protists and fungi are all cellular, living organisms. They have a DNA genome and make machinery to produce their own proteins. They are divided into two main groups based on their cell structure: Prokaryotes and Eukaryotes.
Prokaryotes
Bacteria and Archaea are prokaryotes (“pro” = before, “karyote” = nucleus). They are single cells (unicellular) with a circular DNA genome that floats around in the cytoplasm. Many prokaryotes have one or more smaller circles of DNA called plasmids that carry additional genes. Bacteria and archaea have a very similar cell structure (Figure 3). They do not have a nucleus or membrane-bound organelles. Some prokaryotes have tail-like structures called flagella, which they use to swim through liquid, or fimbriae which enable them to stick to surfaces.
Labelled diagram of a prokaryotes cell: Plasmid DNA, Chromosomal DNA, Ribosomes, Fimbriae, Capsule, Cell wall, Plasma membrane, Cytoplasm and Flagella
Figure 3: Labelled diagram of a bacterium showing the main features of a prokaryotic cell
Bacteria
Bacterial cells are mostly circular (coccus, plural cocci) or rod-shaped (bacillus, plural bacilli), but a few have spiral or corkscrew shapes. Another defining features is the use of peptidoglycan as a component of their cell walls. You almost certainly have millions of Escherichia coli bacteria (Figure 4) in your lower intestine. Most strains of E. coli are harmless, but a few can cause serious food poisoning that can be fatal.