Bacteria

Characteristics of Bacteria

Mostly single-celled

No nucleus or membrane bound organelles

Circular chromosomes

Cell walls

Reproduce asexually & sexually

Anaerobic or aerobic

Heterotrophic or autotrophic

Structure of a Representative Bacterial Cell

Outer capsule offers protection

Stiff cell wall made of peptidoglycan

No membrane-bound organelles (some free ribosomes present)

Chromosome is a single loop of DNA called a plasmid.

Often have one or more flagellum (for locomotion) and many pili (hair-like structures to stick to surfaces)

Cell Shapes

Spherical are called COCCUS

Rod are called BACILLUS

Spiral are called SPIRILLUM or SPIROCHETE

Coccus

Cocci that live as…

• Separate cells = Monococci

• In Pairs = Diplococci

• Linear Chains = Streptococci

• Grapelike clusters = Staphylococci

Streptococcus

Causes Strep Throat

Bacillus

E. coli

Spirochetes

The spirochete Borrelia burgdorferi is a tick-borne parasite responsible for Lyme disease in humans!

Blacklegged ticks are often carriers of Borrelia burgdorferi

An infected tick may transmit Lyme Disease during the act of attaching and biting their host

Gram Stain

Bacteria can be classified by their reaction to a dye made of crystal violet and iodine called GRAM STAIN

Bacteria- Cell Wall Structure

Bacteria are divided into two groups based upon the composition of their cell walls.

Gram positive : two layers (lipid, peptidoglycan – sugar/amino acids network)

Gram negative : three layers, lipid, peptidoglycan, and lipopolysaccharide.

Cellular respiration

How our cells make energy!

Equation: Sugar (glucose) + Oxygen 🡪 Carbon dioxide + Water + ENERGY

Types of Respiration

Aerobic

• Grows in presence of oxygen – eukaryotic cells

Anaerobic

• Grows in absence of oxygen – mostly prokaryotic, sometimes eukaryotic

Obligate Aerobes

• MUST have oxygen to live

Obligate Anaerobe

• Must NOT have oxygen present to live

Facultative Anaerobes

• Can grow with or without oxygen – carries out fermentation when

oxygen is absent

Autotrophs

they can make their own food by photosynthesis. E.g cyanobacteria

Heterotrophs

they get their nutrients from eating other organisms. E.g. E.coli

chemotrophs

rely on carbon or sulfur containing compounds for energy

Cyanobacteria

Photosynthetic bacterium

Bluish-greenish color

Contain membranes that carry out the process of photosynthesis

Can survive in extremely hot environments and even extremely cold environments

Why not a plant?

• Can be unicellular

• Prokaryotic (no nucleus and membrane-bound organelles)

Binary Fission in Bacteria

a rapid form of asexual reproduction and cell division used by prokaryotes (bacteria and archaea) and some single-celled eukaryotes. A single organism replicates its DNA and splits into two identical daughter cells

Sexual Reproduction - Conjugation

Extension of pilus from donor cell and binding to recipient cell

Retraction of pilus and fusion of cell membrane

Transfer of single strand of plasmid DNA and replication of complementary strands

Seperation of cells

Endospores

A type of dormant cell forms (sometimes for years) when conditions are unfavourable.

Exhibit no signs of life

Resistant structure that forms around the chromosome when cell is under some sort of environmental stress such as:

• High temperatures

• Irradiation

• Strong acids

• Disinfectants