Viruses and bacteria

Bacteria The word bacteria is so familiar that we will use it as a common term to describe prokaryotes. Prokaryotes come in many sizes and shapes, they are unicellular organisms that lack a nucleus. Classified into two kingdoms….Eubacteria and Archaebacteria

Eubacteria The larger of the two kingdoms Live almost everywhere…water, land, and within the human body. Very diverse with many different lifestyles.

Eubacteria They contain a cell wall which is made of a carbohydrate called peptidoglycan. Also have a cell membrane and cytoplasm. Some include flagella for movement. The pili are involved in cell-to-cell contact.

Archaebacteria They are alike to eubacteria in the fact that they are small, lack nuclei, and have a cell wall but chemically they are quite different. They LACK the carbohydrate called peptidoglycan in their cell walls. The DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria. Scientists reason that archaebacteria my be the ancestors of eukaryotes.

Archaebacteria They live in harsh environments. Some produce methane gas. They can live in oxygen free environments. Some live in thick mud, intestines of animals, hot springs, or extremely salty environments.

Identifying Prokaryotes Prokaryotes are identified by characteristics such as Shape Chemical Nature of Cell Walls Movement How they obtain energy.

Prokaryotes by Shapes Rod-Shaped prokaryotes are called bacilli

Prokaryotes by Shapes Spherical prokaryotes are called cocci

Prokaryotes by Shapes Spiral shaped prokaryotes are called Spirilla

Prokaryotes by Shapes

Prokaryotes by Shapes

Prokaryotes by Movement Some move some do NOT Some have flagella while others lash, snake, or spiral forward. Still others glide slowly along a layer of slime like material they secrete.

Prokaryotes by Metabolic Diversity Bacteria will vary depending on their source of energy and whether or not they use oxygen for cellular respiration. Heterotrophs or Autotrophs

Prokaryotes that are Heterotrophs Some heterotrophic prokaryotes must take in organic molecules for both energy and a supply of carbon they are called chemoheterotrophs. Most animals (humans too) are chemoheterotrophs. A smaller group of heterotrophs prokaryotes are called photoheterotrophs. These organisms are photosynthetic BUT they also need to take in organic compounds such a carbon sources.

Prokaryotes that are Autotrophs Some groups of autotrophs called photoautotrophs use light energy to convert carbon dioxide and water to carbon compounds and oxygen in a process similar to that of green plants. These live in an environment where light is abundant like near the surfaces of lakes, streams and oceans. Ex: cyanobacteria

Prokaryotes that are Autotrophs Other prokaryotes make organic carbon molecules from carbon dioxide but do NOT require light. They are called chemoautotrophs. Instead, they use energy directly from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron. Some chemoautotrophs live in deep in the darkness of the ocean. They obtain energy from hydrogen sulfide gas that flows from hydrothermal vents on the ocean floor.

Prokaryotes- Energy Bacteria need a constant supply of energy. This energy can be released by the process of cellular respiration and fermentation or BOTH. Obligate Aerobes- require constant source of oxygen Ex; Mycobacterium tuberculosis…cause tuberculosis Obligate anaerobes- must live in the absence of oxygen. Ex: Clostridium botulinum found in soil…it can grow in canned food because it does not require oxygen Facultative anaerobes- can survive with or without oxygen. Because of this they can live just about anywhere. Ex: E.coli—lives anaerobically in the large intestines and aerobically in sewage or contaminated water.

Prokaryotes- Binary Fission When a bacterium has grown so that it has nearly doubled in size, replicates its DNA and divides in half, producing 2 daughter cells. This is known as binary fission. Does not exchange genetic info….asexual reproduction.

Prokaryotes- Conjugation During Conjugation, a hollow bridge forms between two bacterial cells, and genes move from one cell to the other. This transfer of genetic information increases genetic diversity in populations of bacteria.

Prokaryotes- Spore Formation During harsh conditions some bacteria have developed a structure called a spore. This spore will enclose a portion of the bacteria’s DNA and cytoplasm. It can remain dormant for months or years until more favorable conditions. This allows the bacteria to survive. Ex: Bacillus anthracis…which causes the disease anthrax is one such bacteria.

Importance of Bacteria Bacteria are VITAL to maintaining the living world. Some are producers that capture energy by photosynthesis. Others are decomposers that break down the nutrients in dead matter and the atmosphere. Still other bacteria have human uses.

Decomposers Decomposers help the ecosystem recycle nutrients, therefore maintaining equilibrium in the environment. Other organisms like insects and fungi are also decomposers. Bacteria also help in sewage treatment. Bacteria help to break down complex compounds in the sewage into simpler ones.

Nitrogen Fixers Remember earlier in the year we discussed the importance of Nitrogen Fixing Bacteria in the process of Nitrogen Fixation. The bacteria takes N2 out to the atmosphere and converts it to NH3 (ammonia) which then can be used by plants and passed on to various consumers. The knobs pictured here provides a source of nutrients for the bacteria which in turn produce ammonia helping the plants.

Humans Uses for Bacteria Used in the production of food and beverages. Some bacteria can be used industry… cleaning up oil spills. Bacteria can help to remove waste from water Some help to synthesize drugs and chemicals.

Humans Uses for Bacteria The adult intestine contains around 2-4 pounds of bacteria. This bacterial load is 10 times greater than the number of cells within our body. In real numbers, since we are about 75 trillion cells we have approximately 750 trillion bacterial cells within our body. It is astonishing to think about our bodies in such a manner, but we are literally living, breathing bacterial reservoirs.

Viruses!! Viruses can be very difficult to understand. A biologist, Wendell Stanley in 1935 inferred that viruses were NOT alive. Viruses are particles of nucleic acid, protein, and in some cases lipids. Viruses differ widely in terms of size and structure They all enter living cells and once inside use the machinery of the infected cell to produce more viruses.

Viruses!! Most viruses are so small then cannot be seen without an electron microscope. A typical viruses is composed of a core of DNA or RNA surrounded by a protein coat called a capsid. The simplest viruses contain only a few genes whereas the most complex may have more than a hundred genes.

Viruses!! The capsid includes proteins that enable a virus to enter a host cell. Once inside the, the viral genes are expressed. Sometimes the genetic program causes the host cell to make copies of the virus, and in the process the host cell is destroyed. Because the virus must bind to certain proteins on a cell surface and then use a host’s genetic system MOST viruses are highly specific to the cells they infect.

Viruses!! Plant viruses infect plant cells Animal viruses usually only infect certain related species Viruses that infect only bacteria are called bacteriophage.

Virus Structures Bacteriophage

Virus Structures Tobacco Mosaic Virus

Virus Structures Influenza Virus

Viral Infection Once the virus is inside the host cell two different process may occur. Lytic Infection or Lysogenic Infection

Viral Infection Lytic Infection- a virus enters a cell , make a copy of itself, and causes the cell to burst. Lysogenic Infection-, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cells DNA The viral DNA that is embedded in the host’s DNA is called a prophage. It may remain in the host cell for many generations before becoming active. Assignment- Draw, color, and label Figure 19.10 on page 481

Retroviruses Some viruses contain RNA as their genetic information are called Retroviruses. When they infect a cell they must use their RNA to create a DNA copy, which can then be inserted into a host cell. They get their name “retro” meaning backwards because usually we go from DNA to RNA and in this cause it goes backwards…RNA to DNA The virus that causes acquired immune deficiency syndrome (AIDS) is a retrovirus.

Diseases caused by Bacteria and Viruses Bacteria and viruses are everywhere in nature. Its pathogens--disease causing agents that get all the attention. Bacteria can cause disease in one of two ways. 1. The bacteria damage the cells and tissues of the infected organisms directly by breaking down the cells for food. Ex: Tuberculosis 2. Other bacteria release toxins that travel throughout he body interfering with the normal activity of the host. Ex: Strep throat and diphtheria

Preventing Bacterial Disease Some bacterial diseases caused by pathogenic bacteria include Lyme disease, tetanus, strep throat and tooth decay. Many such disease can be prevented by stimulating the body’s immune system with a vaccine. A vaccine is a preparation of weakened or killed pathogens. When injected into the body, a vaccine sometimes prompts the body to produce immunity to the disease.

Preventing Bacterial Disease Antibiotics can also be used once the bacterial infection does occur. Antibiotics are compounds that block the growth and reproduction of bacteria. Penicillin and tetracycline are antibiotics. The dramatic increase in human life expectancy during the past two centuries can be attributed to the better understanding on how to prevent and cure bacterial infections.

Controlling Bacteria Although most bacteria are harmless and many are beneficial, the risks of bacterial infection are great enough to warrant efforts to control bacterial growth. There are various methods used to control bacterial growth, including sterilization, disinfectants, and food processing.

Viral Disease in Humans Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium. The virus will attack and destroy certain cells in the body, causing symptoms. Unlock bacterial diseases, viral diseases cannot be treated with antibiotics. The best way to protect against viruses is prevention often by the use of vaccines. The symptoms of the infections can often be treated but NOT the viruses.