Bacte Structures

• Bacteria have been around for a very long time. In fact, they are the oldest known forms of life on earth. The earliest fossils are of prokaryotes, a group of organisms in which bacteria are a part of. These fossils date back to over 3.5 billion years ago.
• Bacteria have evolved into a variety of different types since then. They have also adapted to a range of different environments; they can live inside the human body, at the north pole, and even at the bottom of the ocean.
• Divisions of Microbiology


  • Virology - study of viruses
  • Parasitology - study of protozoans and helminths
  • Mycology - study of fungi (yeasts, molds)
  • Phycology - scientific study of algae
  • Bacteriology - study of bacteria
• Viruses


  • Small intact infectious agents
  • Can only reproduce inside a cell they have infected
  • Consists of a core of RNA or DNA surrounded by protein, sometimes an envelope of glycoprotein
• Virology


  • In the traditional sense, it is the scientific discipline dealing with the biology of viruses including molecular biology and biochemistry, and viral diseases including physiology, epidemiology, and clinical aspects of viruses
  • In a more modern sense, it encompasses the study of ecology, evolution of viruses, interaction among viruses and other microorganisms, and the ability of viruses to deliver their own and heterologous genetic information into cells
• Virus particle or virion


  • Composed of the viral code proteins enclosing the viral genome which may be surrounded by a lipid envelope
  • When a virion infects a cell, this leads to profound changes of cellular homeostasis, and in turn, alteration of organ functions
• Protozoans


  Unicellular eukaryotic organisms, enclosed in a membrane, and contain visible organelles
• Helminths


  Multicellular parasites, worms (tapeworms, roundworms, flatworms), also have a microscopic stage in their life cycle
• Parasitology


  • The study of the interaction between parasites and their hosts
  • Parasitologists tend to concentrate on eukaryotic parasites such as lice, mites, protozoans, and worms, while prokaryotic parasites and other infectious agents are the focus of fields such as bacteriology, microbiology, and virology
  • Parasites cause millions of deaths and billions of infections in humans every year, but parasites of crops and animals can have equally devastating effects by disrupting global food supplies and people's livelihoods
• Protozoa


  • Single-celled eukaryotes
  • Similar to animals in nutrient needs and cellular structure
  • Live freely in water, some live in animal hosts
  • Asexual (most) and sexual reproduction
  • Most are capable of locomotion by pseudopodia, cilia, or flagella
• Protozoa


  • Entamoeba histolytica
• Transmission of protozoa

  • Protozoa that live in a humans' intestine are typically transmitted through a fecal-oral route, e.g. contaminated food or water or person-to-person contact
  • Protozoans that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector, e.g. through the bite of a mosquito or a sandfly
• Fungi


  • Unicellular or multicellular, thick cell wall
  • Develop from spores or fragments of hyphae
• Mycology


  • The study of fungi and its importance to us and to ecology, and conservation is perhaps unsurpassed by any other branch of the biological sciences
• Algae


  • Mainly aquatic (fresh/saltwater), contain chlorophyll, carry out photosynthesis
  • Some species produce neurotoxins which can concentrate in fish or shellfish and cause poisoning when eaten by humans
• Phycology


  • The study of algae in its many forms
  • Algae are a very primitive plant, and were one of the first types of plants to evolve photosynthetic capabilities which allows the plant to use its green chlorophyll to turn carbon dioxide and water into food with energy from the sun
  • Algae are primarily aquatic plants that lack the structures that terrestrial plants use to stand upright
• Bacteria


  • Are relatively simple, single-celled (unicellular) organisms
  • Live freely in the environment
  • Multiple by binary fission
  • Eubacteria (true bacteria); archaebacteria (ancient bacteria) - different cell walls
• Bacteriology


  • Bacteria are single-celled organisms that lack a nuclear membrane, are metabolically active and divide by binary fission
  • Medically, they are a major cause of disease
  • Bacteria multiply at rapid rates and different species can utilize a variety of hydrocarbon substrates including phenol, rubber, and petroleum
  • The importance of bacteria in every field of medicine cannot be overstated
  • The discipline of microbiology evolved from the need of physicians to test and apply the germ theory of disease and from economic concerns relating to the spoilage of foods and wine
• Bacterial size


  • 0.2 - 2 microns in width or diameter
  • Up to 1 - 10 microns in length

  
• The largest known bacterium is Thimargarita namibiensis, with spheroidal diameters from 100 - 750 microns
• Spherical bacteria as small as 50 - 500 nm in diameter have been reported
• The human body is full of bacteria and in fact it is estimated to contain more bacterial cells than human cells. Most bacteria in the body are harmless, and some are even helpful. Relatively small number of species cause disease.
• Prokaryotes


  • Unicellular organisms that lack membrane-bound structures (the most noteworthy of which is the nucleus)
  • Prokaryotic cells tend to be small, simple cells measuring around 0.1 - 5 um in diameter, or usually 0.2 - 2 um in diameter
  • In prokaryotic cells, DNA bundles together in a region called the nucleoid
  • Prokaryotes can be split into two domains, bacteria and archaea
• Eukaryotes


  • Organisms whose cells have a nucleus and other organelles enclosed by a plasma membrane
  • Organelles are internal structures responsible for a variety of functions such as energy production and protein synthesis
  • Eukaryotic cells are large, around 10 - 100 um, and complex
  • While most eukaryotes are multicellular organisms, there are some single-celled eukaryotes
• Bacterial morphology is extremely diverse. Specific shapes are a consequence of adaptive pressures, optimizing bacterial fitness. Shapes affect critical biological factors, including nutrient acquisition, motility, dispersion, stress resistance, and interactions with other organisms.
• Bacterial Morphology


  • Rods or Cocci (Cocci = spherical, Bacilli = rods)
  • Curved or spiral (Spirochete)
  • Filamentous (Very long thin filament-shaped bacteria, some of them form branching filaments resulting to a network of filaments called the mycelium)

  
• Bacterial shapes


  • Rods or Cocci
  • Curved or spiral
  • Filamentous

  
• Filamentous bacteria


  Very long thin filament-shaped, some form branching filaments resulting in a network called mycelium

  
• Bacterial size: 0.2 - 2 microns in width or diameter, up to 1 - 10 microns in length

  
• Bacterial cells are much smaller than human cells, including human red blood cells which are on average 7 micrometers in diameter
• Bacterial shapes

  • Bacilli = rod-shaped
  • Cocci = spherical
  • Spirochete = spiral

  
• Cocci


  Round cells, sometimes slightly flattened when adjacent to one another
• Bacilli


  Rod-shaped bacteria

  
• Spirillum


  Curved bacteria ranging from gently curved to corkscrew-like spiral, many are rigid and capable of movement

  
• Spirochetes


  Long, slender and flexible spiral bacteria
• Bacterial arrangements of cocci


  • Singly
  • In pairs
  • Groups as tetrads, clusters, or in chains

  
• Cocci in tetrads


  • Aerococcus
  • Pediococcus
  • Tetragenococcus
• Cocci in chains (streptococci)


  • Streptococcus pyogenes
  • Streptococcus dysgalactiae
• Cocci in clusters (staphylococci)


  • Staphylococcus aureus
• Cocci in cubes of 8 cells (sarcinae)


  • Sarcina ventriculi
  • Sarcina ureae