Bacteria What are Prokaryotes Prokaryotes are singlecelled organisms

Bacteria

What are Prokaryotes? • Prokaryotes are single-celled organisms that do not have membrane-bound organelles • They have adapted to live in almost every environment • They are generally found in three shapes Baccilus (rod Coccus shaped) (sphere shape) Spirillum (spiral shape)

Kingdoms of Prokaryotes • Archaea – Found in extreme environments – Structurally different from bacteria • Bacteria – Most prokaryotes are in this group – Can be found virtually anywhere!

Bacterial Structure • Bacteria have genetic material in the form of a single loop of DNA that is clustered in a mass called a nucleoid • Bacteria also have ribosomes and many enzymes • Bacteria have cell membranes and cell walls made of peptidoglycan – Gram positive bacteria have a thick layer of peptidoglycan – Gram negative bacteria have a thin layer of peptidoglycan

Bacterial Structure • Bacteria move by rotating their flagella • Bacteria stick to surfaces with pili

Obtaining Energy & Nutrients • Bacteria differ in how they obtain energy and nutrients • Photoautotrophs get their energy from sunlight – Cyanobacteria were responsible for most of the oxygen on earth • Chemoautotrophs can get their energy from inorganic sources • Heterotrophs get their energy from other organisms (alive or dead)

Reproduction and Adaptation • Bacteria reproduce through binary fission – When a single cell divides into two identical new cells

Reproduction and Adaptation • Bacteria can exchange genetic material through conjugation – During conjugation, a pilus from one bacterium attaches to a second bacterium – The cells then join and exchange genetic material – Benefit: Creates genetic diversity which increases the chance of survival in a changing environment

Reproduction and Adaptation • Some bacteria survive harsh conditions by forming thick-walled structures called endospores – They form inside bacteria – They surround the DNA and protect it from harsh conditions – When harsh conditions end, endospore can disassemble and bacteria can thrive

Bacteria & Humans • Pathogenic (disease-causing) bacteria are responsible for diseases such as Strep Throat and Pneumonia • One can take antibiotics to cure a bacterial infection – Antibiotics interfere with the peptidoglycan cell wall of bacteria • It is important to take antibiotics as prescribed to avoid antibiotic resistance