BACTERIA Bacteria Cells are prokaryotic and amongst the

BACTERIA

Bacteria • Cells are prokaryotic and amongst the smallest known cells ( length 0. 5 -20 µm ). • Lack a nucleus • DNA is naked, a single loop not bound in a chromosome • May contain plasmids (small circular fragments of DNA) • Have ribosomes, but no other organelles. • DNA present as a long circular molecule.

Structure of a Bacteria

Classification • All bacteria are prokaryotes, which can be placed in one of two kingdoms: • Archaebacteria: “Ancient Bacteria” • Archaebacteria “True Bacteria”

Archaebacteria • “Archae” means primitive or early • Oldest organisms on the plant ~ 3 billion yrs old • Live in extreme conditions: Environments in which no other organisms can survive

Environments of Archaebacteria • These bacteria are characterized as living in extreme conditions that have: • • • High temperatures (Thermophiles) Low temperatures (Psychrophiles) High Salt concentrations (Halophiles) High acidity Environments with no oxygen (anerobic)

Archaebacteria Thermophilic bacteria thrive in volcanic vents Halophilic bacteria thrive in salty lakes

Eubacteria • All other bacteria. • Strong cell walls and less complicated genetic makeup. • Live in many habitats • Most common form of life on earth • Can be bad (pathogens) or good (digestion) • Organisms: Bacteria, Cyanobacteria

How to Classify Bacteria • Shape • Cell walls • How they move • How they obtain Energy

Cell Shape • One way that bacteria can be identified is by their shape: Lactobacilli: rod-shaped Rod-shaped, called Bacilli Spirochaeta: spiral Spiral, called Spirilla or Spirochetes Enterococci: spherical Spherical

Coccus • Spherical shaped bacteria are called Cocci Single cells - monococci Pairs - diplococci Chains - streptococci

Bacillus • Rod shaped Bacteria are called Bacilli Exists as: Single Cells In pairs (diplobacilli) In chains (streptobacilli).

Spirilla • Spiral shaped bacteria are called Spirilla • Spirillum (Singular) Plural is spirilli. Exist only as single cells.

Cell Wall • The chemical nature of a cell wall can be studied by a method known as Gram Staining • Hans Christian Gram: inventor of Gram Staining

Gram Staining • Gram stains contain of two dyes • Crystal Violet (Purple) • Safranine (Red) • Gram-positive bacteria: cells with only 1 thick layer of carbohydrate and protein molecules took up the crystal violet dye. • Gram-negative bacteria: cells wall contains a second layer of lip and carbohydrate took up the crystal violet dye.

GRAM STAIN It is the most important differential stain used in bacteriology because it classified bacteria into two major groups: a)Gram positive: Appears violet after Gram’s stain b) Gram negative: Appears red after Gram’s stain

Bacterial Movement • Bacteria can be identified by studying how them move: • Some bacteria propel themselves by the means of 1 or more whip-like structures called a flagella • Some bacteria produce a thick layer of slime to glide about • Others remain stationary

How bacteria obtain Energy • Autotrophs: Organisms that make their own energy • Phototrophic Autotrophs: Bacteria that get there energy from sunlight • Chemotropic Autotrophs: Bacteria that obtain their energy from inorganic molecules – Inorganic molecules: Hydrogen sulphide, nitrites, sulphur and iron

Examples of Autotrophic Bacteria Phototrophic autotroph: Cyanobacteria Chemotrophic Autotrophs: Ecoli bacteria

How Bacteria obtain Energy • HETEROTROPHS: Energy is obtained from other organisms • Chemotrophic heterotrophs: obtain energy by dissolving and absorbing organic material • Phototrophic heterotrophs : obtain sunlight for energy, but need organic compound for nutrition.

Examples of Heterotrophic Bacteria Chemotrophic heterotroph: Salmonella

Bacterial Respiration and Fermentation • Bacteria need a constant supply of energy to perform their life activities • Energy is supplied by the process of: – Respiration: A process that involves oxygen and the breakdown of food molecules to release energy – Fermentation: the process that enables cells to carry out energy production in the absence of oxygen

Bacterial Respiration • Bacteria can be classified into three categories based on their need for oxygen 1. Obligate aerobe: Must have O 2 to live 2. Obligate anaerobes: Must live in O 2 free environment 3. Facultative anaerobes: Can live with or without O 2

RECAP QUESTIONS How would this bacteria be classified according to shape? Is this bacteria a Gram-positive or Gram-negative bacteria?