BACTERIA Bacteria All bacteria share several common characteristics

BACTERIA

Bacteria �All bacteria share several common characteristics �Unicellular (although some stick together in colonies) �Prokaryotic – no nucleus, lack most cell organelles �Single chromosome �Reproduce through binary fission �Need moist environment �Have rigid outer wall that give it shape

Two Kingdoms or Two Domains �Archaebacteria �Eubacteria �occupy environmental �modern species extremes �Thermoacidophiles �Halophiles �Methanogens �probable ancestor of Eukaroyotes �have different RNA and gene products �includes most of the bacteria encountered in daily life

Archaebacteria �Desended from one of the oldest groups of living organisms on earth �Live in areas of such extreme conditions that nothing else survives there

3 major groups Thermophiles � Live in areas of more than 45 C � Some obtain energy from metabolizing sulfur compounds � Live near sulfur hot springs � Enzyme Taq polymerase (from Thermus aquaticus) is used in molecular genetics (DNA replication) Methanogens �Grow in areas without oxygen �Use CO 2 and H 2 O to produce methane �Live in volcanic deepsea vent and mammalian intestines �Used to help digest sewage and oil spills

Halophiles �Live in areas that are very saline such as salt flats and evaporation ponds �Have a bright red pigment that allow to capture sunlight for energy �Used for cancer reasearch

Eubacteria �The most common member of this Kingdom is Escherichia coli �Live in human intestines helping with food digestion and some vitamin synthesis �In too high levels it can be dangerous

�Each new E. coli is about 1 m in length (0. 00000 1 m) �A line of 250 could be seen by the naked eye § A distinction of this kingdom is the structure of the cell wall, however not all have a cell wall § They have a polymer called peptioglycan

�The two types of Eubacteria (with or without a cell wall) can be distinguished by a Gram Strain �Cells are stained with crystal violet (purple dye) �Dye is fixed, cell is “washed” with a decolourizer �Stained again with safranin (red dye) • Those with peptioglycan retain the purple colour (Gram Positive) while those without lose the purple and so take on second stain pink (Gram Negative) • (Staph - +ve , E. Coli –ve)

Streptococcus

Gram Negative

Characterized by 3 shapes A) Cocci spherical --B) bacilli rod-shaped -------C) Spirilla spiral

Bacterial Shape

Configuration �After they divide some cells stay together in groups �If they form a chain they are given the prefix strepto �Ie. Streptococcus mutans (tooth decay)

�If they form a cluster they are given the name staphylo �Ie. Staphylococcus aureus (found on skin)

Streptobacillus

Bacterial Shape staphylococcus streptococcus diplococcus

diplobacillus staphylobacillus streptobacillus

Streptococcus

Streptobacillus

Spirochetes

Helical rods

Tetrads

Typical Bacterial Characteristics �Flagella- whip-like locomotor structure �Pili-hollow tube for attachment or exhange of DNA during conjugation �Cell membrane lies inside wall carries on metabolism and synthesis �Plasmid ring of DNA that may be exchanged between bacteria and may direct antibiotic production

4

• Capsule- for attachment and protection, sticky with various polysaccharides , may cause disease. • Pilis- hollow tubes for attachment or exchan of DNA (conjugation) • Motility- by flagella with some ability to mo towards food • Genome- DNA one large circular chromosom and smaller rings of DNA called PLASMIDS • Endospores- resistant stage for survival of harsh conditions

Capsule- for attachment and protection, sticky with various polysaccharides , may cause disease. Pilis- hollow tubes for attachment or exchange of DNA (conjugation)

Nutrition �Autotrophs – make their own food from inorganic substances �Photosynthetic – convert CO 2, H 2 O and light energy into carbohydrates �Chemosynthetic – use chemical reactions to provide them with energy �Heterotrophs – obtain their energy by consuming other organisms (i. e. Dead, decaying organisms, or by living as parasites on living tissues)

Respiration �Anaerobic �does not require it �Aerobic �Requires O 2

Reproduction �Asexually through binary fission �i. e. Pyrodictium abyssi �Sexually through Conjugation �i. e. Salmonella

Short life cycle 20 min-3 hrs. doubling time

Binnary Fission

Binary Fission

Conjugation �Genes are exchanged via a sex pilus

Spore Formation Endospores- resistant stage for survival of harsh dry or hot environments

Bacterial Pathogens CAUSE DISEASE �Endostoxins- protein or other chemical toxins found within the microbe released when cell dies. �Exotoxins- released by pathogen

How we Control Bacteria �Temperature- exceed range of tolerance autoclave- heat under pressure pasteurization-heat to below 100 degrees C. refrigiration- slows only, not good for psychrophilic �UV light- destroys DNA �Chemical antisepic- on living tissue disinfectant-on inanimate objects antibiotic-produced by living things

Koch's postulates (or Henle-Koch postulates) �Are four criteria designed to establish a causal relationship between a causative microbe and a disease. �The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890. �Koch applied the postulates to establish the etiology of anthrax and tuberculosis, but they have been generalized to other diseases.

KOCH’S POSTULATE �Isolate the suspected pathogen and grow in pure culture �Inoculate a healthy host �Look for symptoms �Re-isolate and compare to original pathogen