Bacteria and Archaea

1 um

Average size of a bacteria

100 to 750 um

Size of Thiomargarita Namibiensis

0.05 to 0.2 um

Size of Nanobacteria

Coccus

bacteria that is spherical, oval, bean-shaped, pointed in shape

Bacillus

bacteria that are rod, cylindrical, filamentous and club-shaped

Vibrio

curved shaped bacteria

Mycoplasmas

Display extreme variations in shape due to lack of cell walls

Diplococci

cocci growing in pairs

Tetrads

cocci arranged in groups of four

Staphylococci and micrococci

irregular clusters of cocci

Streptococci

chains of a few to hundreds of cells

Sarcina

cubical packet of 8, 16, or more cells

Diplobacilli

pairs of bacilli cells with their ends attached

Streptobacilli

chains of bacilli

Palisides

cells of a chain remain partially attached and fold back, creating a side-by-side row of cells

Spirilla

occasionally found in short chains; corkscrew-like

Spirochetes

rarely remain attached after cell division; long, slender spiral-shaped bacteria that have flexible walls and are capable of movement

Flagella and axial filaments

appendages that provide motility

Fimbriae, pili, and nanowires

appendages that provide attachment points or channels

Polar arrangement

flagella are attached at one or both ends of the cell

Monotrichous

single flagellum at one end

Lophotrichous

small bunches or tufts emerging from the same site

Amphitrichous

flagella at both poles of the cell

Peritrichous

flagella are dispersed randomly over the surface of the cell

Chemotaxis

movement in response to chemical signals

Positive chemotaxis

movement of a cell in the direction of a favorable chemical stimulus

Negative chemotaxis

movement of a cell away from a repellant or potentially harmful compound.

Phototaxis

movement in response to light

Run

- counterclockwise movement of the flagella

- cell swims in a smooth, linear direction toward a stimulus

Tumble

- flagellum reverses direction, causing the cell to stop and change course

- Repellants cause numerous tumbles

periplasmic flagella (axial filaments)

- two or more long coiled threads found in spirochetes

- internal flagellum enclosed between the cell walls and the cytoplasmic membrane.

- impart a twisting or flexing motion to the cell.

Fimbriae

- small, bristle-like fibers sprouting off the surface of certain species of bacteria

- most contain protein

- tendency to stick to each other and to surfaces

- responsible for the formation of biofilms

- what e. coli use to adhere to epithelial cells

Pili

- Long, rigid, tubular structure made of pilin protein

- Only found in gram-negative bacteria

- Used in conjugation

Conjugation

partial transfer of DNA from one cell to another

S layer

- thousands of copies of a single protein linked together

- provides protection from environmental conditions

- only produces in hostile environments

Glycocalyx

repeating polysaccharide units that may or may not include protein

Slime Layer

- Forms loosely around the cell

- Protects the cell from loss of water and nutrients

Capsule

- More tightly bound to a cell than a slime layer

- Denser and thicker than a slime layer

- formed by many pathogenic bacteria

- protect bacteria against phagocytic white blood cells.

Biofilms

- example is plaque on teeth protect bacteria

- infect long-term indwelling artificial devices

1884 by Hans Christian Gram

When was gram staining developed and who developed it?

Gram-positive bacteria

- Thick cell wall composed of peptidoglycan

- Inner cytoplasmic membrane

Gram-negative bacteria

- Outer membrane

- Thin cell wall

- Inner cytoplasmic membrane

Cell wall

- helps determine the shape of a bacterium

- provides strong structural support to keep the cell from bursting or collapsing due to osmotic pressure.

Peptidoglycan

- Found in the cell walls of most bacteria

- Unique macromolecule composed of glycan chains cross-linked with short peptide fragments.

- Provides a strong but flexible support framework

Gram-positive cell wall

Thick, homogenous sheath of peptidoglycan 20 to 80 nm thick

Teichoic and lipoteichoic acid

- Resposible for cell wall maintenance

- Enlargement during cell division

- Acidic charge on cell surface.

Mycolic Acid

- a.k.a cord factor

- very-long chain fatty acid

- contributes to pathogenicity of organisms

- makes them resistant to certain chemicals and dyes

acid-fast stain

used to diagnose tuberculosis and leprosy

Mycoplasmas

- Naturally lack a cell wall

- Membrane is stabilized by sterols and is resistant to lysis

- Pleomorphic shape, range from 0.1 to 0.5 um, ranging from filamentous to coccus or doughnut-shaped

Gram-negative outer membrane

contains specialized polysaccharides and proteins

Lipoproteins

anchor the outer membrane to peptidoglycan

Endotoxin

stimulates fever and shock reactions

Porin proteins

- Completely span the outer membrane

- Only allow relatively small molecules to penetrate

- Size can be altered to block the entrance of harmful chemicals

- Act as a defense against certain antibiotics

Cytoplasm

- gelatinous solution contained by the cytoplasmic membrane

- prominent site for the cell's biochemical and synthetic activities

- 70 to 80% water

- Complex mixture of sugars, amino acids, and salts

- Also contains the chromatin body, ribosomes, granules, and fibers that act as a cytoskeleton.

Bacterial Chromosome

- Single circular strand of DNA

- Aggregated in a dense area called the nucleoid

- DNA is tightly coiled around basic protein molecules to fit into the cell compartment.

Plasmids

- Nonessential pieces of DNA

- Separate, double-stranded circles of DNA

- Duplicated and passed on to offspring during replication

- Confer protective traits

- Important agent in genetic engineering

Ribosomes

- Made of RNA and protein

- Dispersed throughout the cytoplasm, often found the chains

Svedberg (S) units

- measurement of the relative size of cell parts through sedimentation during centrifugation

Bacterial ribosomes

70S Ribosomes

Eukaryotic ribosomes

80S Ribosome

Inclusion Bodies

- Storage sites for nutrients during periods of abundance

- Vary in size, number, and content

Cytoskeleton

- long polymers of proteins similar to eukaryotic actin

- arranged in helical ribbons around the cell just under the cytoplasmic membrane.

- contribute to cell shape

- potential target for antibiotic development

Endospores

Withstand hostile conditions and facilitate survival

Vegetative cell cycle

metabolically active and growing

Endospore cycle

inert, resting condition

Sporulation

spore formation induced by environmental conditions

Bacillus anthracis

Causes Anthrax

Clostridium tetani

Causes tetanus (lockjaw)

Clostridium perfringes

Causes gas gangrene

Clostridium botulinum

Causes botulism

Archaea

- Most primitive of all life forms

- Most closely related to cells that originated 4 billion years ago

- Live in habitats that are similar to the extremes found anciently—heat, salt, acid, pH, pressure, atmosphere

- Methane producers, hyperthermophiles, extreme halophiles, and sulfur reducers.

Methanogens

- convert CO2 and H2 into methane gas (CH4)

- Common inhabitants of anaerobic swamp mid, bottom sediments of lakes and oceans, and the digestive systems of animals

- Gas produced in swamps may become a source of fuel

- May contribute to greenhouse gases and global warming

Extreme Halophiles

- Require salt to grow

- Some can multiply in 36% NaCl that would destroy most cells

- Exist in inland seas, salt lakes, salt mines, and in salted fish

- Use a red pigment to synthesize ATP in the presence of light

Psychrophiles

grow at very low temperatures

Hyperthermophiles

grow at very high temperatures

Phenotypic

the basis for early classification: shape, cultural behavior, and biochemical reaction

Bergey's Manual of Systematic Bacteriology

- Comprehensive view of bacterial and archaea relatedness

- Combines phenotypic information with rRNA sequencing for classification

- Now available online

Bergey's Manual of Determinative Bacteriology

- Based entirely on phenotypic characteristics

- Categorizes bacteria by traits commonly assayed in clinical, teaching, and research labs

- Widely used by microbiologists who need to identify bacteria but need not know their evolutionary backgrounds

- Useful for students of medical microbiology

Gracilicutes

gram-negative cell walls, thin-skinned

Firmicutes

gram-positive cell walls, thick and strong

Tenericutes

lack a cell wall, soft

Mendosicutes

Archaea

Aerobic

use oxygen in metabolism

Anaerobic

do not use oxygen in metabolism

Facultative

may or may not use oxygen

Bacterial species

A collection of bacterial cells which share an overall pattern of similar traits

Subspecies, strain, or type

Bacteria of the same species that have differing characteristics

Serotypes

Representatives of a species that stimulate a distinct pattern of antibody responses because of distinct surface molecules