Biology of Prokaryotes Two Basic Types of Cells

Biology of Prokaryotes

Two Basic Types of Cells Prokaryotes Lack a nucleus and membrane-bound organelles Have a nucleoid instead of a nucleus Examples are all bacteria and cyanobacteria

Two Basic Types of Cells Eukaryote Cells Contains a nucleus Has membrane-bound organelles Examples are plant cells, protists, fungi, and animal cells

Domain: Bacteria Domain bacteria is divided into two separate kingdoms: Eubacteria Archaebacteria

Eubacteria Larger of the two kingdoms Live almost anywhere Contain peptidoglycan in their cell walls Example: E. coli

Archaebacteria main differences is their chemical make-up Lack petidoglycan and also have membrane lipids Live in extremely harsh conditions DNA sequence are more like eukaryotes than eubacteria Methanogens: archaebacteria that live in oxygen-free environments

Structure and Function Major Structures in Prokaryote cells are: Cell Wall Cell Membrane Cytoplasm Ribosomes Sometimes a capsule, pili, endospores, and flagella

Cell Wall Most Prokaryotes have cell walls Bacteria cell walls contain peptidoglycan Protein carbohydrate compound Archaeal cell walls do not contain peptidoglycan but contain pseudomurein, a compound made up of unusual lipids and amino acids

Cell Wall

Cell Membrane and Cytoplasm Bacterial and Archaeal cell membranes are lipid bilayers but the types of lipids differ between the two. The cytoplasm in both contain: Ribosomes DNA Small organic and inorganic molecules Ions

DNA Prokaryotic DNA is a single closed loop of double-stranded DNA attached to the cell membrane Some prokaryotes also have plasmids. Small circular, self-replicating doublestranded DNA

Capsules and Pili Many bacteria have an outer capsule made up of polysaccharides that protects the cell against drying, pathogens, or harsh chemicals Pili are short, hairlike proteins on the surface of some bacteria Use these to connect to each other and to surfaces such as a host cell

Endospores Some Gram Positive bacteria can form a thick-coated resistant structure called an endospore.

Prokaryotic Movement Many prokaryotes have long flagella to help them move towards food sources or away from danger

Bacteria Shapes 3 shapes of bacteria cells: 1) Bacillus Rod-shaped bacteria 2) Coccus Round or circular-shaped bacteria 3) Spirilla Spiral-shaped bacteria

Bacteria Shapes

Strepto vs. Staphylo Strepto: bacteria cells are aligned in chains Staphylo: bacteria cells are aligned in clusters

Gram Staining 2 types of Eubacteria cell walls Gram staining is used to tell them apart Gram stain consists of two dyes: One violet (the primary stain) One red (the counterstain)

Gram Staining Process 1) Violet stain is applied to the bacteria culture first. This stains the peptidoglycan walls 2) Alcohol wash 3) The red counter stain is applied second

Gram Stain Results Gram Staining results in either a grampositive or gram-negative bacteria Gram-Positive Bacteria Have thick peptidoglycan walls that retain the dark color of the violet stain Gram-Negative Bacteria Much thinner cell walls Alcohol dissolves the lipid and removes the dye from the walls The counterstain then makes these bacteria appear pink or bright red

Nutrition and Metabolism Prokaryotes obtain nutrients from nonliving organisms or by utilizing the products or bodies of living organisms Heterotrophs-obtain carbon from other organisms Autotrophs-obtain carbon from CO 2 Chemotrophs-get energy from chemicals in the environment

Metabolic Diversity Chemoheterotrophs Photoautotrophs Chemoautotrophs

Prokaryotic Habitats Different species live in different environments Temperature requirements range from 0 -110 degrees celsius Most grow best at a neutral p. H, 7.

Reproduction and Recombination Reproduction of bacteria is done by binary fission (asexual reproduction) Bacteria cell doubles in size, replicates its DNA, and divides in half producing two identical “daughter” cells MITOSIS!!!!

Reproduction and Recombination Genetic Recombination occurs in 3 ways: Transformation: Taking in DNA from the outside environment Conjugation: exchanging DNA with other bacteria via pili Transduction: transmission of bacterial DNA via viruses

Releasing Energy Like all other organisms, bacteria need a steady supply of energy. This supply is done by either cellular respiration or fermentation Organisms that require a constant supply of oxygen in order to live are called obligate aerobes Bacteria that do not require oxygen and may be killed by it are called obligate anaerobes Bacteria that can survive with or without oxygen are known as facultative anaerobes Have the ability to switch from CR to Fermentation. This allows them to live almost everywhere!

Importance of Bacteria are vital to maintaining the living world Some bacteria are decomposers that help break down dead organic matter in the ecosystem Others help in the process of nitrogen fixation (process of converting nitrogen gas into a form plants can use) Lastly, humans have specific uses for bacteria Production of food and beverages Some bacteria can digest petroleum, making them useful in oil spills Some bacteria live in our stomaches to help break down foods and make a number of vitamins our body could not produce by itself

Bacteria and Health Human diseases may result from endotoxins or exotoxins produced by bacteria or from the destruction of body tissues

Bacteria and Health Endotoxins Toxin that occurs in the outer membrane of Gram negative bacteria and that is released when the bacterial cells break apart Exotoxin Potent, extracellular toxin secreted by some gram positive bacteria

Antibiotics and Antibiotic Resistance Mutation in the DNA of bacteria may cause a resistance to an antibiotic Cells with mutant gene have selective advantage when antibiotic is present Mutant cells take over population when normal cells die

Food Hygiene Preventative Measures: Wash all fruits and vegetables before eating them Selecting, storing, cooking and handling food properly Frequently wash hand utensils in hot, soapy water