Ch. 27: Bacteria and Archaea Modern/regular/eubacteria and the ancient methanogens Prokaryote  cells with cell membranes, cytoplasm/cytosol, DNA in the form of one circular chromosome and many plasmids, and 70s ribosomes. Shapes are cocci, bacilli, spirillum May have cell wall, flagella, cilia and other structures

Adaptations Adaptations to extremes of climate from freezing to boiling to acidic and salty. (species specific ranges) Salt tolerant up to 32% Hot springs - thermophiles Near frozen waters at arctic Acid conditions; 0.03 pH !! – acidophiles 3 million Rads of radiation

Fig. 27-1

Structure and functions contribute to success Unicellular but may aggregate into colonies Cell walls; Gram positive and gram negative based on peptidoglycans and lipids Capsules; waxy layer that helps avoid antibiotics Fimbriae (like velcro) and pili (trade plasmids) Motility; cilia and flagella and taxis; roughly 50% are capable of movement – at relatively fast speeds Plasmids

layer Carbohydrate portion of lipopolysaccharide Outer membrane Fig. 27-3 Carbohydrate portion of lipopolysaccharide Outer membrane Peptidoglycan layer Cell wall Cell wall Peptidoglycan layer Plasma membrane Plasma membrane Protein Protein Gram- positive bacteria Gram- negative bacteria 20 µm (a) Gram-positive: peptidoglycan traps crystal violet. (b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.

Internal and Genomic Organization Not usually any internal, membrane-bound structures May have specialization built into PLASMA MEMBRANE 70s ribosomes; smaller than eukaryotic, solid (erythromycin and tetracycline) Nucleoid region One, circular chromosome, hundreds of genes, fills central portion, Many plasmids – copies of frequently or currently used genes

Adaptations of reproduction Binary fission – one cell divides into 2 those into 4 those into 8, etc. Can occur every hour at optimal conditions, some species every 20 minutes, typical is 24 hours 1 bacteria could create a colony outweighing Earth in 3 days…. Obvious checks and balances here. Nutrient supply Toxins/ poison selves Competition Space - pressure

Bacterial Populations They are very small organisms 0.5 – 5 mm ( eukaryotic are 10-100 mm) They reproduce by binary fission They have very short generation times ENDOSPORES can survive harsh conditions and survive for centuries MSU study looked at 20,000 generations in 8 years – evidence of evolution Simpler – but not inferior or primative On Earth for over 3.5 billion years now

Diversity Three events lead to diversity Rapid reproduction Mutation Most variety in sexually reproducing species is from arrangement/ shuffling of alleles during meiosis Insertions, deletions, base pair substitutions Mutations still very RARE, but sheer numbers of organisms and time per generation means more are expressed Mutation More variety in ribosomal RNA between 2 strains of E.coli than between human and platypus Genetic recombination Next page

Genetic Recombination Transformation Bacteria are able to absorb genetic information from their surroundings Transduction Bacterial genes are also spread between bacteria populations by viruses known as bacteriophages Conjugation Pili bridge bacteria and they trade plasmids F factor and R factor

Fig. 27-11-4 Phage DNA A+ B+ A+ B+ Donor cell A+ Recombination A+ A– B– Recipient cell A+ B– Recombinant cell

Fig. 27-13 F plasmid Bacterial chromosome F+ cell F+ cell Mating bridge F– cell F+ cell Bacterial chromosome (a) Conjugation and transfer of an F plasmid Recombinant F– bacterium Hfr cell A+ A+ A+ A+ F factor A– A+ A– A– A+ A– F– cell (b) Conjugation and transfer of part of an Hfr bacterial chromosome

Metabolic adaptations (table 27.1)

Metabolism Oxygen Metabolism Nitrogen Metabolism Metabolic Cooperation Obligate aerobes Obligate anaerobes Facultative anaerobes Nitrogen Metabolism N is essential for amino acids Atmospheric N isn’t highly useable Microbes ‘fix’ nitrogen into nitrate, nitrites and ammonium ions that are useable Metabolic Cooperation Colonies of cells that fix nitrogen and produce oxygen so that neighboring area is hospitable Ocean floor and dental plaque 

Molecular Systematics Previously bacterial classification (systematics) used motility, shape, nutrition and gram staining Molecular systematics has drastically changed the classification – Much more diverse than assumed 6000+ species/strains ID and named A soil sample could contain over 10,000 species Horizontal transfers of genes blur “root” for this region of the tree of life Two main branches are Archaea and Bacteria

Groups of Bacteria Eukarya Archaea Bacteria

Subgroup: Alpha Proteobacteria Fig. 27-18a Subgroup: Alpha Proteobacteria Alpha Beta Gamma Proteobacteria Delta 2.5 µm Epsilon Rhizobium (arrows) inside a root cell of a legume (TEM) Subgroup: Beta Proteobacteria Subgroup: Gamma Proteobacteria 1 µm 0.5 µm Nitrosomonas (colorized TEM) Thiomargarita namibiensis containing sulfur wastes (LM) Subgroup: Delta Proteobacteria Subgroup: Epsilon Proteobacteria B. bacteriophorus 10 µm 5 µm 2 µm Fruiting bodies of Chondromyces crocatus, a myxobacterium (SEM) Bdellovibrio bacteriophorus attacking a larger bacterium (colorized TEM) Helicobacter pylori (colorized TEM)

GRAM-POSITIVE BACTERIA Fig. 27-18i CHLAMYDIAS SPIROCHETES 2.5 µm 5 µm Chlamydia (arrows) inside an animal cell (colorized TEM) Leptospira, a spirochete (colorized TEM) CYANOBACTERIA GRAM-POSITIVE BACTERIA 50 µm 1 µm 5 µm Hundreds of mycoplasmas covering a human fibroblast cell (colorized SEM) Two species of Oscillatoria, filamentous cyanobacteria (LM) Streptomyces, the source of many antibiotics (colorized SEM)

Positive Roles of Bacteria Decomposers Symbioses Mutualism Commensalism – normal flora (parasitism – not positive) Chemical recycling Nitrogen Oxygen Carbon Research and Technology Food (cheese) and beverages Waste water treatment Genetic engineering

Negative Impacts of Bacteria Parasitic bacteria that cause disease are called PATHOGENS Opportunistic Exotoxins and endotoxins