Kingdom Monera - The Bacteria

Transcription

1 Chapter 8 The World of Microbes Kingdom Monera - The Bacteria Bio-significance- The down side: Disease of plants crop loss Disease of animals loss of livestock and herds Human disease cavities to The Plague The up side: Decomposers recycle nutrients like carbon, oxygen, and sulphur back into food chain. Reduces waste (carrion, detritus). Nitrogen fixers make nitrogen available to food chain. Fermentation bread, cheese, yogurt, other milk products. Waste-water management. Research MOST BACTERIA ARE EITHER HARMLESS OR BENEFICIAL; ONLY A (RELATIVELY) SMALL NUMBER ARE PATHOGENIC. Characteristics: Prokaryotic. Single celled No membrane-bound organelles. Especially significant is the lack of a membrane bound nucleus. DNA is therefore freefloating in the cytoplasm. Single chromosome, which is normally circular. 1

2 Most reproduce by asexual reproduction: binary fission (simply splitting in two) but can exchange DNA with other bacteria through pili (thin extensions). Some bacteria can even pick up free floating DNA in the environment ancd incorporate it in their own genetic material. Great metabolic diversity. Bacteria essentially live in every corner of the globe. Including boiling mud, hot springs, coal mines, polar ice caps, hot water vents. Morphology See handout. Identification and classification Shapes Coccus (pl. cocci) spherical Bacillus (pl. bacilli) rod shaped Spirilla spiral shaped Arrangement Single Chains Strepto Clusters Staphylo- 2

3 Biologists group bacteria into one of two Sub-Kingdoms: Archaebacteria or old bacteria normally live in anaerobic conditions, high salt/temperature/acidity (idea being that these were the conditions of early Earth) Eubacteria or true bacteria essentially everything else. However, because there are so many different kinds of bacteria with so few kinds of shape and arrangement possibilities, classification is difficult and therefore depends largely on how they acquire nutrition and the style of respiration they use. Classification Based On Respiration Obligate aerobes must have oxygen to survive. E.g. Mycobacterium tuberculosis (Tuberculosis) Obligate anaerobes can only grow in absence of oxygen. E.g. Clostridium spirillum Faculatitive anaerobes don t care. Will grow whatever Types of Respiration Aerobic respiration. Bacteria get their energy by turning sugar into CO 2 and water Anaerobic respiration (Fermentation). Bacteria get their energy by turning sugar into CO 2 and some other organic molecule such as Alcohol. Lactic acid Acetone Acetic acid Methane Modes of Nutrition 3

4 Heterotrophs when nutrients are derived from another organism Parasites if taken from living organisms. Most diseasecausing bacteria use this. Saprophytes if taken from dead and decaying organisms Autotrophs when nutrients are made by the bacteria. Photosynthesis when light energy is used to change simple carbon (like CO 2 ) to a sugar. Chemosynthesis when (because there is no light) chemical energy is used. Reproduction Binary fission - splitting into two equal parts following DNA duplication. Most common form of replication Conjugation - A fine tube pilus (pl. pili), which is a cytoplamic bridge, extends from a donor bacterium to a recipient bacterium of the same mating type. A small circle of DNA (plasmid) is transfered and incorporated into recipient DNA. Enteric bacteria e.g. E.coli and Salmonella. Endospores - During times of stress, some bacilli bacteria form protective coats around genetic material. Spore becomes dormant 4

5 and is super resistant to heat so it is not easily destroyed. When good conditions occur, bacterium emerges and carries on. Read p218. Do p219 Questions (except #3) or p220 Case Study Read p221 Human diseases Antibiotics and Bacterial Resistance Some points to ponder: 1) Bacterial resistance is conferred through R-factors which are proteins which inactivate certain drugs. 2) R-factors are coded for by plasmids and are the result of mutations(?). 3) Plasmids are swapped freely between bacteria. Recombination of plasmids creates bacteria with multiple resistances. 4) Antibiotics remove only htose bacteria who do not have the plasmid for the right R-factor. 5) Removal of competiting bacteria allows resistant bacteria free access toresources and so they proliferate Natural Selection. 5

6 Potential result: A bacteria that is resistant to every antibiotic known to man. A word: Bardenpho Kingdom - Protista Characteristics: eukaryotic - have membrane bound nucleus and other organelles unicellular, microscopic aquatic and marine environments Three Groups of Protista Phytoplankton - (plant-like) producers - autotrophic {significant contributor to oxygen cycle} Zooplankton - (animal-like) consumers - heterotrophic Gymnomycota - (fungal like) rotters saprophytic 6

7 Phytoplankton plant-like protists Divided into three groups: 1) Brown algae and diatoms 2) Dinoflagellates 3) Euglenids oddball organism, has both animal-like and plantlike characteristics. Zooplankton animal-like protests (a.k.a. protozoa). Wide size range 2 µm to 5 cm. Many different species (st. bacteria) Normally asexual reproduction (fission) but can form resting cells (cysts) 7

8 Classification is based on: Mode of locomotion Types of organelles Life cycle Mode of reproduction Nutrition o Holozoic engulf food o Saprozoic absorb pre-digested or soluble nutrients Free-living or parasitic AskJeeves.com>amoebas organisms>#4 Introductory courseware Phylum Sarcodina (Amoeba) 8

9 Phylum Ciliaphora (Paramecium) 9

10 Phylum Sporozoa (Plasmodium) 10

11 Gymnocota 11