Bacterial Cell Structure Fig. 4.1

Cytoplasm dense gelatinous solution of sugars, amino acids, & salts 70-80% water serves as solvent for materials used in all cell functions

Chromosome single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell DNA is tightly coiled around a protein, aggregated in a dense area called the nucleoid

DNA temperature melting Bacteria classification G + C

plasmids small circular, double-stranded DNA free or integrated into the chromosome duplicated and passed on to offspring not essential to bacterial growth & metabolism may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins used in genetic engineering- readily manipulated & transferred from cell to cell

Ribosomes made of 60% ribosomal RNA & 40% protein consist of 2 subunits: large & small procaryotic differ from eucaryotic ribosomes in size & number of proteins site of protein synthesis All cells have ribosomes.

Inclusions, granules intracellular storage bodies vary in size, number & content bacterial cell can use them when environmental sources are depleted Examples: glycogen, poly-b-hydroxybutyrate, gas vesicles for floating, sulfur and polyphosphate granules

Fig 4.10

Cytoplasmic membrane Protoplast Spheroplast L forms

4 groups based on cell wall composition Gram positive cells Gram negative cells Bacteria without cell walls Bacteria with chemically unique cell walls

Gram positive Gram negative

Gram positive Gram negative Fig 4.16

Lipopolysaccharide O-antigen Highly variable n Core Heptoses Ketodeoxyoctonic acid Lipid A Glucosamine disaccharide Beta hydroxy fatty acids (Hydroxy myritic Acid)

LPS function Endotoxins Exotoxins

Gram positive wall

Gram negative cell wall

Peptidoglycan

Cytoplasm Cytoplasm Periplasmic space Lipoteichoic acid Peptidoglycan-teichoic acid Cytoplasmic membrane Cytoplasm Lipopolysaccharide Porin Outer Membrane lipoprotein Periplasmic space Inner (cytoplasmic) membrane Cytoplasm

Gram Positive Cell Envelope Lipoteichoic acid Peptidoglycan-teichoic acid r r r Cytoplasmic membrane Cytoplasm

Glycocalyx Coating of molecules external to the cell wall, made of sugars and/or proteins 2 types capsule - highly organized, tightly attached slime layer - loosely organized and attached Functions attachment inhibits killing by white blood cells Receptor (K antigen)

2 Types of Glycocalyx

Biofilms

Flagella

lophotrichous Monotrichous amphitrichous peritrichous

Fig 4.2b

Fimbrae Adhesion to other cells and surfaces

pili rigid tubular structure made of pilin protein found only in Gram negative cells Functions joins bacterial cells for DNA transfer (conjugation) adhesion

Conjugation

endospores

Important components in endospore: Calcium Dipicolinic Acid

Sporulation

The endospore

Major Taxonomic Groups of Bacteria Gracilicutes – gram-negative cell walls, thin-skinned Firmicutes – gram-positive cell walls, thick skinned Tenericutes – lack a cell wall & are soft Mendosicutes – archaea, primitive procaryotes with unusual cell walls & nutritional habits

Grwth in Bacteria Temperature Nutrients pH Osmotic pressure

Temperature Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism Maximum temperature – highest temperature that permits a microbe’s growth and metabolism Optimum temperature – promotes the fastest rate of growth and metabolism

3 temperature adaptation groups

Bacterial Metabolism Phototroph Chemotroph Photoautotroph (Photolitotroph) Photoheterotroph (Photoorganotroph) Chemotroph Chemoautotroph (Chemolitotroph Chemoheterotroph (Chemoorganotroph)

Stages of metabolism in chemoheterotrophic bacteria Digestion Absorption (Passive and active transportation) Preparation for oxidation Oxidation

Oxygen requirements

Fermentation Incomplete oxidation of glucose or other carbohydrates in the absence of oxygen Uses organic compounds as terminal electron acceptors Yields a small amount of ATP Production of ethyl alcohol by yeasts acting on glucose Formation of acid, gas & other products by the action of various bacteria on pyruvic acid

Fermentation

Binary division

Growth Curve

Continuous Culture, Chemostat Chemostats are a means of keeping a culture in log phase indefinitely. Continuous Culture, Chemostat

Methods in bacterial identification Microscopic morphology Macroscopic morphology – colony appearance Physiological / biochemical characteristics Chemical analysis Serological analysis Genetic & molecular analysis G + C base composition DNA analysis using genetic probes Nucleic acid sequencing & rRNA analysis

Bacterial Colonies Standard Bacterial Count Colony-Forming Units Plaque-Forming Units Spread Plate Pour Plate Soft-Agar Overlay

Solid Medium