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Biology 112 BACTERIA AND VIRUSES.  Smallest and most common microorganisms  Unicellular organisms that lack a nucleus  They can be divided into two.

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Presentation on theme: "Biology 112 BACTERIA AND VIRUSES.  Smallest and most common microorganisms  Unicellular organisms that lack a nucleus  They can be divided into two."— Presentation transcript:


2  Smallest and most common microorganisms  Unicellular organisms that lack a nucleus  They can be divided into two separate groups  Eubacteria  Archaebacteria PROKARYOTES

3  Live almost everywhere  Usually surrounded by a cell wall that protects it from injury as well as determines its shape  Cell wall contains peptidoglycan, a carbohydrate  Cell membrane inside the cell wall that surrounds the cytoplasm  Some have a second membrane which further protects it from damage EUBACTERIA

4  Have cell walls, lack nuclei and lack the peptidoglycan that is present in eubacteria  There are different lipids existing in their cell membranes  The DNA sequencing is more similar to eukaryotes than prokaryotes  May be the ancestors of eukaryotes  Most live in harsh environments, including mud, digestive tracts, volcanoes ARCHAEBACTERIA

5  Shape  Rod-shaped (bacilli), spherical (cocci), spiral/corkscrew (spirilla)  Composition of Cell Walls  Thick peptidoglycan walls (gram positive) or thinner walls with a second outer lipid layer (gram negative)  Movement  Some do not move at all, others have flagella, which are whiplike structures while others still lash, snake, spiral and glide IDENTIFYING PROKARYOTES

6 Heterotrophs (ex. E coli) Autotrophs (ex. Cyanobacteria) FOURTH IDENTIFYING CHARACTERISTIC OF PROKARYOTES (OBTAINING ENERGY)

7  Heterotrophic Prokaryotes  Eat other organisms for energy as well as a supply of carbon  Called chemoheterotrophs  Others are autotrophs to obtain their energy but also eat other organisms for their necessity for carbon  Called photoheterotrophs HOW PROKARYOTES OBTAIN ENERGY - HETEROTROPHS

8  Use light energy to convert carbon dioxide and water to carbon compounds and oxygen  Found where light is available  Photoautotrophs  Make organic carbon molecules from carbon dioxide but do not require light  Use energy from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur or iron  Present in harsh environments  Chemoautotrophs HOW PROKARYOTES OBTAIN ENERGY - AUTOTROPHS

9  They undergo cellular respiration, fermentation or both  Those that require a constant supply of oxygen are called obligate aerobes  Those that do not require it (or may even be killed by the presence of oxygen) are called obligate anaerobes  Those that can survive with or without oxygen are called facultative anaerobes  Do not require it but are not harmed by it either  As a result, they can survive almost anywhere HOW PROKARYOTES RELEASE THEIR ENERGY

10  How fast they grow and reproduce depends mostly on availability of food and the production/elimination of waste products  When a prokaryote has doubled in its size, it may divide in half through a process called binary fission (daughter cells are identical to single parent cell – asexual reproduction)  Conjugation occurs when a bridge forms between two cells and genetic material can be passed between the two  Spore formation, called endospores, may form within a prokaryote  A thick wall forms around the DNA and a portion of the cytoplasm  Spore may remain dormant until more favorable conditions occur GROWTH AND REPRODUCTION

11  Critical for maintaining the living world  Some are producers as well as decomposers  Others have uses in human survival  Decomposers  Bacteria recycles nutrients which maintains balance in the environment  Without them, sewage systems would not be able to eliminate all its waste and disease would spread IMPORTANCE OF BACTERIA

12  Nitrogen fixers  Plants need nitrogen to make amino acids (building blocks of protein)  Nitrogen (N 2 ) must be changed to ammonia (NH 3 ) or other nitrogen compounds (nitrates) before it can be used by living things  This process is known as nitrogen fixation IMPORTANCE OF BACTERIA

13  Human uses  Food industry  Lactobacillus is used for the preservation of dairy  Industry  Sulfate-reducing bacteria in the petroleum industry  Waste removal  Bacteria that converts waste into fuel  Mining  Bacteria that leaches copper from mines  Synthesize drugs and chemicals for improved health  Vaccines IMPORTANCE OF BACTERIA – HUMAN USES

14  Viruses are composed of parts of nucleic acid, protein and lipids  Reproduction only occurs by infecting living cells  Great variety in their size and appearance  All viruses infect cells the same way – by entering healthy cells and once inside, use the organelles of the infected cell to produce more viruses  It is typically composed of DNA, RNA and a protein coat VIRUSES

15  Protein coat is also called a capsid  Contains proteins that enable the virus to enter the host cell  Binds to receptors on a healthy cell and “tricks” the cell into allowing it to enter  Once inside, viral genes are exposed to the cell  The healthy cell ‘reads’ the genetic information and then may, as a result, get destroyed in the process  The host cell may also make copies of the virus STRUCTURE OF A VIRUS

16  Viruses are highly specific to the host cell it is infecting  As a result, viruses which target plants may not contain the proteins in their capsids to gain entry to an animal cell  Viruses that attack bacteria are called bacteriophages VIRUSES ATTACK DIFFERENT ORGANISMS

17  Some viruses replicate themselves immediately once inside the host cell and kill the cell  Others do not replicate in such a way that destroys the host cell immediately  Lytic Infection  Virus enters cell, replicates itself, and causes the cell to burst  Destroys the cells DNA, uses the cell to make viral proteins and viral DNA, then releases viral particles  Lysogenic Infection  Incorporation of the viruses DNA with the host cell DNA and replicates along with the host cell’s DNA  Viral DNA is called a prophage which may lay dormant for an indefinite amount of time VIRAL INFECTION

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