CH 4 PROCARYOTES: BACTERIA & ARCHAEA (“ARCHEAH”) First cells were a type of archaea that were possibly related to modern ones that live on sulfur compounds in geothermal ocean vents—very adaptable cell structures Under light microscopes bacteria appear simple and w/o features—electron scopes in the 40’s—50’s proved otherwise Found that bacteria had : appendages (flagella, pili, fimbria) Layers to their cell coverings (glycocalyx, cell wall, cell membranes) Objects (NOT organelles!) in their cytoplasm (ribosomes, granules, nucleiod, chromosome)

Bacterial Shapes, Arrangements & Sizes Even if found with another cell, each bacterial cell is independent and capable of carrying out all life processes SHAPES—determined by the cell wall Coccus (cocci)—spherical, ball shaped, but can also be bean shaped, oval or “pointy” Bacillus (bacilli)—cylindrical, rod shaped, many variations according to species Spirillum/spirochete—spiral shaped cylinder, 3 types: Spirillum– rigid, corkscrew Spirochete– flexible, spring-like Vibrio– comma shaped cylinder

Pleomorphism Same species varying in shape and size due to variations in cell wall caused by nutritional or hereditary differences Corynebacterium diphtheriae are rod shaped, but can also be club shaped, swollen, curved, filamentous or round Mycoplasmas lack cell walls, so have extreme shape variations

Arrangements Bacteria can be arranged several ways (fig 4.25) determined by how the cells divide Coccus can be in pairs: diplo Chains : strepto Tetrad: sarcina Irreg. clusters: staphylo Bacillus can be pairs or chains Palisades: diplobacillus that snap at hinge and fold back on each other Spirilla normally do not remain attached after division See fig 4.26 for size comparison

Appendages Common, but not in all species 2 major groups: Motility: flagella For attachment: fimbria and pili FLAGELLA– self-propulsion, made of 3 distinct parts Filament—helical structure composed of proteins, 20 nm in diameter, 1-70 nm in length Hook—curved and tubular, holds the filament, anchored to the cell by the… Basal body—stack of rings that go thru the cell wall to the cell membrane This arrangement allows the hook and filament to rotate 360° in a counter clockwise motion, which moves the bacteria forward Appendages

Flagella, cont. Arranged in 3 ways: polar—flagella attached at 1 or both ends Monotrichous—single flagellum Lophotrichous—small bunches of flagella at same site Amphitrichous—flagella at both ends Second arrangement: peritrichous where the flagella are randomly dispersed over the entire cell Periplasmic flagella are those found in the space between the cell wall and cell membrane and causes the cell to wiggle, twist and flex (spirochetes) Can determine motility by: Put sample INSIDE semisolid media—rapid growth thru entire medium indicates motility Observe using a hanging drop slide (fig 4.4)

Bacteria with flagella are sensitive to their environment Positive chemotaxis—movement toward a favorable chemical stimulus (food) Negative chemotaxis—movement away from a repellant compound Phototaxis—movement in response to light

Appendages for Attachment & Mating Pilus and fimbria provide adhesion, but not locomotion Fimbria are shorter and more numerous strands Pilus are longer and sparser Some pathogens use fimbria to adhere to epithelial cells to cause disease: Gonococcus—gonorrhea in genitourinary tract E. coli—intestinal tract Sex pilus is a special tubular structure made of pilin (protein) used in bacterial conjugation: partial transfer of DNA thru this cytoplasmic connection—only occurs between Gram neg. cells Conjugation does occur between Gram pos. cells, but not with a sex pilus