Lecture 3 - Bacteria PDF

week 2 LECTURE 2 BACTERIA - Constitute a large domain of prokaryotic microorganisms. - There size may range between 1 – 15 microns. Bacteria are the most abundant organisms found on the earth. -Bacteria can be adapted to live in different conditions: 1-in cold places, hot regions. 2- in hi...

week 2 LECTURE 2 BACTERIA - Constitute a large domain of prokaryotic microorganisms. - There size may range between 1 – 15 microns. Bacteria are the most abundant organisms found on the earth. -Bacteria can be adapted to live in different conditions: 1-in cold places, hot regions. 2- in high mountains, in high salt concentration 3- in dry places, in stomach juice (acidity + enzymes). 4- in vinegar (high acidity). 5- in absence of oxygen, in boiling water. Morphology of Bacteria: There are 4 main forms: A. Spherical-shaped: They are subdivided into 6 groups: 1. Micrococci: Which occur as single cells. 2. Diplococci: Which occur in pairs after the cell Divisions in one plane. 3. Tetracocci: Which occur in fours after the cell divides in 2 planes. 4. Sarcinae: Which occur in eights after the cell divides in 3 planes. 5. Streptococci: Which occur in chain like-form after the repeated division of the cell in one plane. 6. Staphyllococci: Which occur in the form of cluster of cells after the cell divides in several planes. B. Rod-shaped: [Bacilli, (sing.) Bacillus] They are small short or long cylinders with tapered or curved ends. They are divided into: 1. Single bacilli: Occur singly 2. Diplobacilli: Occur in pairs. 3. Streptobacilli: Occur in a chain. C. Spiral-shaped: These are divided into 3 groups: 1. Vibriones: Which are comma-shaped. 2. Spirilla: Which are less-twisted. 3. Spirochaetes: Which are much-twisted. D. Filamentous bacteria: (Actinomycetes) - It is formed of branched filaments similar to that of fungi. - Fungi like bacteria. Motility or movement of bacteria: - Bacteria are either motile or non motile. -Most cocci are non motile. -They transfer from one place to another by the movement of the medium they live in (air, water, soil). - Most bacilli and spiral-shaped bacteria are motile. - The motility is either by or creeping swimming Creeping bacteria: - They haven’t any organs of movement. - They move or creep slowly by contractions. - They contract and relax in a worm-like movement. Swimming bacteria: - They move freely in the liquid medium. - They have one or many flagella as organ of movement. According to the number and position of flagella we have different forms which are: 1. Monotrichous: Which has one flagellum at one end. 2. Lophotrichous: Which has many flagella at one end. 3. Amphitrichous: Which has one or more flagella at the 2 ends. 4. Peritrichous: Which has many flagella surrounding the cell. Structure of the bacterial cell: The bacterial cell is formed of: 1. Capsule. 2. Cell wall. 3. Cytoplasmic membrane. 4. Cytoplasm. 5. Flagellum. 6. Fimbriae. 7. Nuclear material. 1- Autotrophic Bacteria These are bacteria which are able to synthesize their own organic food from inorganic substances. They use carbon dioxide for obtaining carbon and utilize hydrogen sulphide (H2S) or ammonia (NH3) or hydrogen (H2) as the source of hydrogen to reduce carbon. These bacteria can be distinguished further into two types as follows: Photoautotrophic Bacteria Chemosynthetic Bacteria 2- Heterotrophic Bacteria These are bacteria which are unable to manufacture their own organic food and hence are dependent on external source. Symbiotic Bacteria Saprophytic Parasitic Bacteria 1- (Autotrophic) Photoautotrophic Bacteria The photoautotrophic bacteria possess photosynthetic pigments in membrane bound lamellae (or thylakoids) and utilize solar energy. The bacterial photosynthesis is different from that of green plants since here water is not used as a hydrogen donor. Hence oxygen is not released as a byproduct. For this reason, the process is described as anoxygenic photosynthesis. 2- (Autotrophic) Chemosynthetic Bacteria These are bacteria which manufacture organic compounds from inorganic raw materials utilizing energy liberated from the oxidation of inorganic substances. Following are the common types of chemo autotrophic bacteria. 1. Nitrifying bacteria which derive energy by oxidizing ammonia into nitrates. Eg: Nitrosomonas, Nitrobacter. 2. Sulphur bacteria which derive energy by oxidizing hydrogen sulphide to sulphur. Eg: Thiobacillus, Beggiatoa. 3. Iron Bacteria which derive energy by oxidising ferrous ions into ferric form. Eg: Ferrobacillus, Gallionella. 2- Heterotrophic Bacteria Symbiotic Bacteria These are bacteria which live in a mutually beneficial association with other organisms. Such bacteria derive the essential nutrients from their host organisms and in that process help the host through some of their biological activities. The most familiar example of symbiotic bacteria are the nitrogen fixing bacteria found in the root nodules of leguminous plants. Bacteria such as Rhizobium and Pseudomonas reside in the root nodules and reduce atmospheric nitrogen directly to ammonia. Parasitic Bacteria These are bacteria which occur in the body of animals and plants, obtaining their organic food from there. Most of these bacteria are pathogenic, causing serious diseases in the host organisms either by exploiting them or by releasing poisonous secretions called toxins. Saprophytic bacteria - bacterium, that lives and feeds on dead organic matter. Reproduction of bacteria: There are 3 types: A. Vegetative reproduction: - This occur by very rapid and simple way of division known as binary fission. - It takes 30 min. – 6 hr. to occur. B. Asexual reproduction: - Occur in unfavorable condition in special types of bacteria. - There are 2 forms: 1. Conidia formation: 2. Endospores: - Endospores can resist high temperature and high acidity and alkalinity. 3. Sexual reproduction: - Not common in bacteria. - Called conjugation. - Occur by the transfer of part of the nuclear material from one cell to another cell to form 2 mutant cells.  Bacteria in the living world I. Bacteria and the Cycles of Matter: 1. The Carbon Cycle 2. The Nitrogen Cycle II. Biological Control III. Bioremediation IV. Anaerobic Sewage Treatment V. Dairy Products VI. Bacteria in Medicine I. Bacteria and the Cycles of Matter 1. The Carbon Cycle: 2. The Nitrogen Cycle:  1. The Carbon Cycle: 1. Carbon Dioxide Fixation into organic compounds by Photoautotrophs (e.g: Green plants, Algae, Cyanobacteria 2. Chemoheterotrophs (e.g: Animals) consume the organic compounds (e.g: plants) and may be eaten by other animals. 3. CO2 is released into the atmosphere through Respiration. Or it may be excreted as waste. 4. When the organisms die, the organic compounds of their bodies are deposited in the soil and decomposed by other microorganisms (eg. Bacteria ) and CO2 is then returned to the atmosphere again. 5. Carbon is stored in rocks, such as Limestone (CaCO3) and is dissolved as carbonate ions (CO3-) in oceans. 6. Carbon is also stored in fossil forms such as Coal and Petroleum 7. Burning such fossil fuels releases CO2. The Carbon Cycle  2. The Nitrogen Cycle: The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. 1. Nitrogen fixation 2. Ammonia Assimilation 3. Nitrification 4. Denitrification The Nitrogen Cycle 1. Nitrogen Fixation  2. Ammonia Assimilation Microbial Decomposition Proteins Amino acids (Dead cells & waste Products) Microbial Ammonification Amino acids Ammonia (NH3)  3. Nitrification Oxidation of Ammonium ions to Nitrite By Autotrophic Nitrifying Bacteria Nitrosomanas NH4 + NO2- Ammonia Oxidation Nitrite Nitrobacter NO2- NO3- Nitrite Oxidation Nitrate (Source of N2 for protein synthesis by plants  4. Denitrification Loss of Nitrogen to the atmosphere as Nitrogen gas by bacteria in Anaerobic Respiration NO3- NO2- N2O N2 Nitrate ion Nitrite ion Nitrous Nitrogen oxide gas  II. Biological Control The use of certain microorganisms and / or their toxins to kill or disable the insect pest of certain crop plants. They called Microbial Insecticides. Such as Bacteria used for the biological control of insects via infection of their digestive tracts. e.g Bacillus thuringiensis For the control of Mosquito- born diseases such as Malaria  III. Bioremediation Bioremediation is a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site. Such as the bioremediation of oil spills. Microorganisms used to perform the function of bioremediation are known as Bioremediators. e.g. Pseudomonas cepacia can decompose toxic waste into harmless residues within 6 months.  IV. Anaerobic Sewage Treatment Sewage treatment is the process of removing contaminants from wastewater. Anaerobic bacteria e.g. (Colistridium) breakdown complex organic compounds in sewage into simple substances such as acetate, lactate, ethanol, CO2, hydrogen, methane.  V. Dairy Products Dairy Products manufactured by the addition of certain bacteria e.g. (Colistridium) to the pasteurized milk to produce:  Butter Milk  Yogurt  Sour Cream  Cheese  VI. Bacteria in Medicine Some Pathogenic Bacteria can cause Human Diseases.  Tooth Decay (Dental Caries): Tooth decay is promoted by bacteria, which adhere to tooth surface and gum margins and contribute to dental plaque. Dental plaque: is a film composed of bacteria , bacterial products and salivary substances. e.g. Streptococcus mutans forms extracellular water- soluble glucans, which assist bacterial adhesion to the tooth. Waste products of bacterial metabolism (eg Lactic acid) cause demineralization in the teeth, permittind bacterial penetration.  Immunity Immunity : is the resistance of the body to the invading microbes, toxins or other foreign bodies There is 2 types of Immunity: I. Innate Immunity II. Acquired Immunity  I. Innate Immunity It is the resistance of certain species of animals to diseases which attack others.  II. Acquired Immunity Which may be Active or Passive. Active Natural Artificial Passive Natural Artificial