Lecture 2: Bacteria PDF

week 2 LECTURE 2 BACTERIA - Constitute a large domain of prokaryotic microorganisms. - There size may range between 1 – 15 microns. Loading… Bacteria are the most abundant organisms found on the eart...

week 2 LECTURE 2 BACTERIA - Constitute a large domain of prokaryotic microorganisms. - There size may range between 1 – 15 microns. Loading… 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 Loading… groups: 1. Micrococci: Which occur as single cells. 2. Diplococci: Which occur in pairs after the cell Divisions in one plane. 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. Vibrions&Spirilla Spirochaetes -Rigidcellwall. -Nonrigidcellwall. -Constantshape. -Differentshapes. -Movebyflagella. -Noflagella. (worm-likemovement) 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. Loading… 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 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. IronBacteria Thepresenceofhighlevels ofironormanganeseinground waterandwellsoftengivesrisetothe growthofanorganismcalledironbacteria. 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: Separationoftheend ofthefilaments Formationofa chainofrounded conidia o о Onfavourable liberation O 4 condition Conidiacan resistdryness 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. ChromosomalDNA FPlasmid ChromosomalDNA 1. Pilius Donor Recipient 2. DNAPolymerase 3. Relaxasome Transferasome FPlasmid FPlasmid Pilius Pilius OldDonor NewDonor Bacteria in the living world I. Bacteria and the Cycles of Matter: 2. The Carbon Cycle