Bacteria/Viruses

• Bacteria have been around for a very long time. In fact, they are the oldest known forms of life on Earth!
• The earliest fossils we know are of prokaryotes. That's a group of organisms that includes bacteria. These fossils are about 3.5 billion years old!
• Since then, bacteria have evolved into a wide variety of types. They have also adapted to many different environments. They can live inside the human body, at the North Pole, and even at the bottom of the ocean!
• There are more bacteria living in your mouth than there are people who have ever lived on Earth!
• Bacteria


  Single-celled organisms
• Bacterial cells are between about 1 and 10 μm long. And most of them are only 1 to 2 μm in diameter.
• 1 μm, or micrometre, is 1 000 times smaller than a millimetre. That is much smaller than the human red blood cell, which is about 7 μm in diameter.
• Pili


  Hair-like structures that help bacteria attach to surfaces and to other bacteria
• Plasmid


  Small, circular, double-stranded molecule of DNA that contains genes that help when the bacteria is in danger, such as when it is exposed to an antibiotic
• Ribosomes


  Little round structures that produce proteins, found floating in the cytoplasm
• Cytoplasm


  Thick, water-based (aqueous) solution containing ribosomes, nuclear materials, salts, nutrients, minerals and enzymes
• Cytoplasmic membrane


  Thin layer of phospholipids and proteins that controls the movement of nutrients in and out of the cell
• Cell wall


  Rigid layer that gives the bacteria its structure and protects the cytoplasmic membrane
• Capsule


  Third layer that helps keep the bacteria from drying out and can also help protect the bacteria (only present in some types)
• Nucleoid


  Made of DNA, RNA and proteins, controls the activity of the cell, found within the cytoplasm
• Flagellum


  Structure that helps the bacteria move around and sense their environment
• There are millions of different types of bacteria in the world.
• Characteristics used to classify bacteria

  • Thickness of cell wall
  • Shape
• Gram staining


  Process used to measure the thickness of cell walls, where thick cell walls keep the violet colour of the dye and thin cell walls do not
• Bacterial cell wall types

  • Gram Positive (thick, appear blue or purple when dyed)
  • Gram Negative (thin, appear pink or red when dyed)
• Bacterial shapes


  • Spherical (cocci)
  • Rod-shaped (bacilli)
  • Spiral-shaped
• Some bacteria are pathogenic, meaning they can make us sick. These include tetanus, typhoid fever, tuberculosis, strep throat, anthrax, and food poisoning.
• Only a small fraction of the bacteria in the world cause us harm. In fact, many bacteria are helpful!
• Examples of helpful bacteria

  • Probiotic bacteria in our digestive system
  • Bacteria used to make food and beverages (vinegar, kombucha, yogurt, chocolate, kimchi, cheese, sourdough bread)
• Bacteria are diverse and interesting living things. People may think of them as things that make us sick, but they do a lot of good for us as well!
• Viruses have a big impact on humans. Coronavirus 2019 (COVID-19), the common cold, the flu, Severe Acute Respiratory Syndrome (SARS) and diseases like Acquired Immunodeficiency Syndrome (AIDS) are all caused by viral infections.
• Viruses are very small, usually 17 to 400 nanometres in diameter, much smaller than a human hair (about 80,000 nanometres wide) and even smaller than bacteria (about 100 times larger).
• Basic parts of a virus

  • Nucleic acid (DNA or RNA)
  • Capsid (protein coat)
  • Envelope (covering made of phospholipids and glycoproteins)
• Main categories of virus shapes

  • Helical
  • Polyhedral
  • Enveloped
  • Complex
• Helical viruses


  Look like long rods, can be rigid or flexible
• Polyhedral viruses


  Many-sided, with capsids that can have different numbers of sides, most have 20 triangular sides and 12 vertices
• Enveloped viruses


  Shaped like spheres, have a protein, fat or carbohydrate coat over their capsid
• Complex viruses


  Have complicated structures, with capsids attached to structures that look like legs (tail fibres)
• Scientists are not sure if viruses are living things or not, as they do not share many characteristics of living things.
• Viruses cannot reproduce on their own, they must live inside a host cell to make more viruses. Hosts can be bacterial, plant or animal cells.
• Virus reproduction (virus life cycle)

  1. Infect host cell

  2. Use host cell to replicate

  3. Release new viruses
• Microbes are tiny living things that are too small to see with the naked eye, and they live in every type of environment, including the ocean.
• Types of marine microbes

  • Bacteria
  • Phytoplankton
  • Fungi
  • Viruses
  • Archaea
  • Protists
  • Rotifers
• Phytoplankton are microscopic creatures that can create their own food through photosynthesis, and they produce much of the oxygen we breathe.
• Phytoplankton are the base of ocean food chains, with zooplankton eating them and then larger animals eating the zooplankton.