Bacteria and Archaea - Wilmington College PDF
Preview Bacteria and Archaea - Wilmington College
9/14/2014 Three domain system: The present tree of life Bacteria and Archaea Chapter 27 Structural and functional adaptations Cell-surface structures contribute to prokaryotic success Cell wall Unicellular Eukaryote cell walls are made of cellulose or chitin Small Bacteria have peptidoglycan Variety of shapes Archaea have polysaccharides and proteins but lack peptidoglycan Cocci Bacilli Spiral Well organized Gram-positive bacteria include Scientists use the Gram stain to classify bacteria by cell –Actinomycetes, which decompose soil wall composition –Bacillus anthracis, the cause of anthrax Gram-positive bacteria have simpler walls with a large –Clostridium botulinum, the cause of botulism amount of peptidoglycan –Some Staphylococcus and Streptococcus, which can be Gram-negative bacteria have less peptidoglycan and an pathogenic outer membrane that can be toxic –Mycoplasms, the smallest known cells More likely to be antibiotic resistant Gram-Positive Bacteria Gram-Positive Bacteria m m 5 2 Streptomyces, the source of many Hundreds of mycoplasmas covering antibiotics (SEM) a human fibroblast cell (colorized SEM) 1 9/14/2014 Cell surface structures Motility Many bacteria exhibit taxis, the ability to move toward or Capsule away from a stimulus Slime layer Chemotaxis Fimbriae Pili Flagella –Formed from from secretory protein system Most motile bacteria propel themselves by flagella scattered Internal Organization and DNA about the surface or concentrated at one or both ends Flagella of bacteria, archaea, and eukaryotes are composed of Lack compartmentalization different proteins and likely evolved independently Specialized membranes perform metabolic functions DNA packaged in a circular chromosome in the nucleoid region Additional rings of DNA called plasmids Chromosome Plasmids 0.2 m 1 m Respiratory membrane Thylakoid membranes 1 m Reproduction and Adaptation Prokaryotes have considerable genetic variation: why? Key features: They are small, reproduce by binary fission, and have short generation times Three factors contribute to genetic diversity: Many prokaryotes form metabolically inactive endospores, –Rapid reproduction which can remain viable in harsh conditions for centuries –Mutation –Genetic recombination Endospore Coat 0.3 m 2 9/14/2014 Transformation and Transduction Conjugation Transformation: Phage Conjugation: process where genetic material is transferred incorporating foreign DNA A B Donor cell between prokaryotic cells from the surrounding environment A B Transduction: movement of genes between bacteria by Sex pilus bacteriophages (viruses that infect bacteria) A Recombination A A B Recipient cell A B Recombinant cell The role of oxygen in metabolism Diverse nutritional and metabolic adaptations have evolved in prokaryotes –Obligate aerobes require O for cellular respiration 2 –Obligate anaerobes are poisoned by O and use 2 Phototrophs obtain energy from light fermentation or anaerobic respiration Chemotrophs obtain energy from chemicals –Facultative anaerobes can survive with or without O 2 Autotrophs require CO as a carbon source 2 Heterotrophs require an organic nutrient to make organic compounds Nitrogen metabolism Nitrogen is essential for the production of amino acids and nucleic acids Prokaryotes can metabolize nitrogen in a variety of ways In nitrogen fixation, some prokaryotes convert atmospheric nitrogen (N) to ammonia (NH) 2 3 3 9/14/2014 Archaea Extremophiles Extreme halophiles Halobacterium Extreme thermophiles Thermophilus aquaticus Methanogens Prokaryotes play crucial roles in the Ecological Interactions biosphere Symbiosis Chemical Recycling larger host and smaller symbiont Chemoheterotrophic Mutualism prokaryotes function as decomposers Commensalism Parasitism Availability of nitrogen, phosphorus, and potassium for plant growth 4 9/14/2014 Prokaryotes have both beneficial and harmful impacts on humans Pathogenic prokaryotes typically cause disease by releasing toxins Mutualistic Bacteria Human intestines are home to about 500–1,000 species of bacteria Pathogenic Bacteria Exotoxins are secreted and cause disease even if the Lyme disease is caused by a bacterium and carried by ticks prokaryotes that produce them are not present Endotoxins are released only when bacteria die 5 m Toxic protein crystals from Bacillus thuringiensis “Bt” Most eukaryotes are single-celled organisms Protists are eukaryotes Protists Eukaryotic cells have organelles and are more complex than prokaryotic cells Most protists are unicellular, but there are some colonial and Chapter 28 multicellular species Structural and functional diversity in Protists, the most nutritionally diverse Protists of all eukaryotes, include: Protists exhibit more structural and functional diversity than Photoautotrophs any other group of eukaryotes which contain chloroplasts Single-celled protists can be very complex, as all biological Heterotrophs functions are carried out by organelles in each individual cell absorb organic molecules or ingest larger food particles Mixotrophs 5 9/14/2014 Endosymbiosis Endosymbiosis is the process in which a unicellular organism engulfs another cell Mitochondria Aerobic prokaryote Plastids Photosynthetic cyanobacterium The plastid-bearing lineage of protists evolved into red and green algae Five Supergroups of Eukaryotes Polyphyletic Group Excavata Chromalveolata Rhizaria Archaeplastida Unikonta Excavates Diplomonads modified mitochondria Lack plastids and most live in anaerobic environments unique flagella Diplomonads Giardia intestinalis, a diplomonad parasite 6 9/14/2014 Parabasalids Euglenozoans Trichomonas vaginalis, a sexually transmitted disease Includes predatory heterotrophs, photosynthetic autotrophs, and parasites A spiral or crystalline rod of unknown function inside their Flagella flagella m 5 Flagella 0.2 m 8 m Crystalline rod (cross section) Undulating Ring of microtubules membrane (cross section) Chromalveolates may have originated by secondary endosymbiosis Alveolates The proposed endosymbiont is a red alga Members of the clade Alveolata have membrane-bounded Includes the alveolates and the stramenopiles sacs (alveoli) just under the plasma membrane The alveolates include Dinoflagellates Apicomplexans Ciliates Flagellum Alveoli m 2 .0 Dinoflagellates Have two flagella and each cell is reinforced by cellulose plates They are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs Toxic “red tides” are caused by dinoflagellate blooms Flagella m 3 7 9/14/2014 Apicomplexans Ciliates Parasites of animals Use of cilia to move and feed Most have sexual and asexual stages that require two or more Large macronuclei and small micronuclei different host species for completion Genetic variation results from conjugation, in which two Plasmodium requires both mosquitoes and humans to individuals exchange haploid micronuclei complete its life cycle Paramecium 50 m Stramenopiles Diatoms Important phototrophs as well as several clades of Unicellular algae with a unique two-part, glass-like heterotrophs wall of hydrated silica Most have a “hairy” flagellum paired with a “smooth” Major component of flagellum phytoplankton and are highly diverse Stramenopiles include diatoms, golden algae, brown algae, Fossilized diatom walls and oomycetes compose much of the sediments known as diatomaceous earth This removes carbon Hairy dioxide from the m Smooth flagellum atotm thoesp ohceeraen afnlodo “rp umps” it 04 flagellum 5 m Golden Algae Golden algae are named for their color, which results from their yellow and brown carotenoids The cells of golden algae are typically biflagellated, with both flagella near one end Most are unicellular, but some are colonial 8 9/14/2014 Alternation of Generations Brown Algae A variety of life cycles have evolved among the multicellular Largest and most complex algae algae All are multicellular, and The most complex life cycles include an alternation of most are marine generations, the alternation of multicellular haploid and Brown algae include diploid forms many species commonly Heteromorphic generations are structurally different, while called “seaweeds” isomorphic generations look similar Alternation of generations Oomycetes Water molds, white rusts, and downy mildews Once considered fungi based on morphological studies Most are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake Their ecological impact can be great, as in potato blight caused by Phytophthora infestans Rhizarians are a diverse group of protists defined by DNA similarities Radiolarians DNA evidence supports Rhizaria as a monophyletic clade Marine protists called radiolarians have tests fused into one Rhizarians include Radiolarians, Forams, and Cercozoans delicate piece, usually made of silica Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis The pseudopodia of radiolarians radiate from the central body Pseudopodia 200 m 9 9/14/2014 Foraminiferans or Forams Cercozoans Porous, generally multichambered shells, called tests Include most amoeboid and flagellated protists with Pseudopodia extend through the pores in the test threadlike pseudopodia Foram tests in marine sediments form an extensive fossil They are common in marine, freshwater, and soil ecosystems record Most are heterotrophs, including parasites and predators Many forams have endosymbiotic algae Chromatophore 5 m Bonnemaisonia Red algae and green algae are the hamifera 20 cm closest relatives of land plants Red Algae Over a billion years ago, a heterotrophic protist acquired a Reddish in color due to an cyanobacterial endosymbiont accessory pigment called phycoerythrin 8 mm Red algae are usually Dulse (Palmaria palmata) multicellular; the largest are Nori seaweeds Red algae are the most abundant large algae in coastal waters of the tropics Unikonts include protists that are Green Algae closely related to fungi and animals Green algae are a paraphyletic group Includes animals, fungi, and some protists The two main groups are chlorophytes and charophyceans This group includes amoebozoans and the opisthokonts Charophytes are most closely related to land plants (animals, fungi, and related protists) Most chlorophytes live in fresh water, although many are marine Other chlorophytes live in damp soil, as symbionts in lichens, or in snow 10
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