Diversity of Living Things 2.1 – Eubacteria and Archaea

Characteristics of All Bacteria Prokaryotic and single-celled No membrane-bound organelles Contain 1 chromosome Reproduce asexually by binary fission

CharacteristicProkaryoticEukaryotic Meaning of namePro means before Karyon means nucleus Eu means true Karyon means nucleus KingdomsBacteria, ArchaeaAnimalia, Plantae, Fungi, Protista SizeSmall (1-10 micrometre)Large ( micrometre) ComplexityLess complex (mostly unicellular) More complex (mostly multicellular) Structure of cell membraneNo nuclear membraneNuclear membrane present DNA structureCircular (usually one chromosome) Not circular (more than one chromosome) OrganellesUsually absentPresent ReproductionUsually asexual reproduction Usually sexual reproduction Oxygen requirementAnaerobicAerobic

Importance of prokaryotes Disease-causing bacteria (called pathogens) are responsible for many human diseases such as tuberculosis, strep throat, cholera and leprosy Ecological role: many are decomposers or producers Live in animals’ intestine and aid in digestion (in humans, they produce vitamin K and B 12 ) Commercial uses: production of cheese, yogourt, soy sauce, chocolate and antibiotics Genetic engineers have used bacteria to produce insulin and human growth hormone

Eubacteria Have lived on Earth for more than 3.5 billion years There are 6 important groups. See Table 1 on p. 48 for key features. Three of these major groups are photosynthetic, proteobacteria and green bacteria photosynthesize differently from plants

Characteristics of bacteria Structure Contain 1 chromosome in form of loop in area called nucleoid (some bacteria also have one or more small loops of DNA called plasmids ) Have one or more flagella for movement and small hair-like structures called pili See Figure 6 on p s_files/image002.jpg jpg

Characteristics of bacteria Structure (cont’d) Cell walls contain peptidoglycan which give it strength Some surrounded by capsule which provides protection

Characteristics of bacteria Shape: – coccus (pl. cocci) = round – bacillus (pl. bacilli) = rod-shaped – spirillum (pl. spirilla)= spiral

Characteristics of bacteria Clusters (groupings) - Diplo- (pairs) - Staphylo – (grape cluster) - Strepto – (linear chain) See Figure 7 on p. 49

Characteristics of bacteria Metabolism - Some autotrophic (via photosynthesis or chemosynthesis), some heterotrophic Respiration - Some obligate aerobes (can’t live without oxygen); some facultative aerobes (can live with or without oxygen); some obligate anaerobes (can’t live with oxygen)

Characteristics of bacteria Reproduction - Binary fission (asexual reproduction) - In most cases, daughter cells are genetically identical to parent cell - Mutations occur occasionally (1000 times as much as eukaryotic gene) which creates genetically different offspring -Conjugation (sexual reproduction) - two cells join to exchange genetic information - copy of a plasmid is passed to another bacterium through a hollow pilus

Conjugation

Characteristics of bacteria Reproduction cont’d - Transformation - when bacteria takes in and uses pieces of DNA from its environment (if DNA came from other species, called horizontal gene transfer)

Characteristics of bacteria Ability to survive: Endospores - Highly resistant structure which forms around nucleus during unfavourable environmental conditions

Bacterial Diseases Cause many diseases (range in severity of symptoms similar to viral diseases) – Ex. Cholera, diptheria, lyme disease, pertussis, tetanus, botulism Some cause disease by producing and releasing toxins (ex. Botulism) Some contain toxins that aren’t released until cell dies (ex. E. coli water contamination) See Table 2 on p. 51

Antibiotics and Antibiotic Resistance Antibiotics are substances used to destroy bacteria Antibiotic resistance is caused when antibiotics are overused or used improperly

Archaebacteria Live in extreme environments, most without oxygen Cell structure is very resistant to physical and chemical disruption Not very well understood yet

Archaebacteria (cont’d) 4 major groups: – Methanogens – Halophiles – Extreme thermophiles – Psychrophiles

Archaebacteria (cont’d) Methanogens -produce methane -live in low-oxygen environments: swamps, marshes, digestive tracts of mammals

Archaebacteria (cont’d) Halophiles -live in extremely salty environments

Archaebacteria (cont’d) Thermophiles -live in extreme heat, 70 to 95 degree Celsius

Archaebacteria (cont’d) Psychrophiles -live in extreme cold, -10 to -20 degree Celsius