What are bacteria?

Bacteria are single celled organisms that lack a nucleus, and multiply by cell division. Are they eukaryotic or prokaryotic cells?

Bacteria can be found virtually everywhere! They are found in the air, soil, water, in and on plants and animals including humans. Did you know? A single teaspoon of topsoil contains approximately 1 billion bacterial cells. The human mouth is home to more than 500 different species of bacteria.

Humans are colonized by many different species of bacteria. Methods of transmission: Saliva, aerosols Blood Skin contact Genital secretions Faecal-oral route Vectors such as mosquitoes Sites of contamination: Eyes Nose and throat Mouth Airways and lungs Skin Stomach and intestines Urinary tract Genital tract

Question: How many bacteria are present per cm 2 on the human skin? Answer: An average of 100,000 bacteria!

Bacteria have: Ribosomes DNA Plasma membrane Cell wall Capsule Flagellum Pili

Bacteria possess a very simple structure: BUT…don’t be fooled! They are an amazingly complex and fascinating group of organisms.

Bacterial Capsule Stain!!! - Capsules enhance the ability of bacteria to cause disease

Bacteria come in a wide range of shapes, sizes and colours! Three main shapes are –1. Bacilli-rod shaped –2. Cocci-sphere shaped –3. Spirilla-corkscrew shaped Two major configurations are: –Strep- chain –Staph- cluster

Examples of various species’ shapes, sizes and colors! BacillusBordetellaClostridiumEscherichia SpirulinaStaphylococcusStreptococcusSalmonella

Gram Stain from a clinical specimen Human White blood cell Bacteria staining as gram positive rods How do we visualize bacteria? Bacterial cells can only be seen using a microscope. Various staining techniques may be used in order to aid this.

How bacteria get ENERGY? Most are HETEROTROPHS –Chemoheterotrophs- use organic molecules for a Carbon and energy source –Humans are chemoheterotrophs too and if we do not handle food carefully, bacteria will get to OUR food before we do. –Photoheterotrophs- use organic molecules for Carbon source and sunlight for energy

How bacteria get ENERGY? Some are AUTOTROPHS –Photoautotroph- use sunlight to convert CO2 and H2O to Carbon compounds and O2 –Chemoautotroph- make Carbon compounds from CO2, but don’t use sunlight, they use energy from chemical reactions

How do they use Oxygen? Obligate aerobes- require O2 (respiration) Obligate anaerobes- must live without O2 (fermentation) Facultative anaerobes- survive with or without O2 (switch between respiration and fermentation)

Reproduction Binary fission- asexual reproduction happens when a bacterium has grown so that it has nearly doubled in size, it replicates its DNA and it divides in half producing two identical daughter cells.

1 bacterium can become 1/2 million in 6-7 hours Binary Fission Based on Harvard Medical School Family Health Guide

Reproduction Conjugation- Exchanging genetic information in which a hollow bridge forms between two bacteria cells and genes are passed. This increases genetic diversity.

Do all bacteria cause disease? Answer = No Only a subset of the thousands of species of bacteria are capable of causing disease and then only in certain circumstances.

Bacteria is VITAL For…… 1.) Decomposing 2.) Converting nitrogen gas into a form plants can use known as Nitrogen Fixation. ALSO………..

Bacteria is VITAL To HUMANS –Health Skin and intestines –Everyday use Industry Food Clean up waste Research

Summary What is bacteria? Does all bacteria look the same? How can we actually “see” bacteria? What are the two ways bacteria consumes energy? How does bacteria reproduce? How is bacteria vital to us?

Diphtheria

Streptococcus

Staphylococcus