OVERVIEW OF MICROBES

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• OVERVIEW OF MICROBES

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DOMAIN ARCHEA

• The Archeabacteria
• are prokaryotes
• differ from the eubacteria
• are the leftovers of the first living organisms
• generally are found in harsh environments

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Some Archeabacteria

• Extreme thermophiles
• Sulfolobus
• Pyrodictium occultum found in the
• Methanogens
• Methanobrevibactor
• Methanobacterium

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• DOMAIN BACTERIA

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Anaerobic chemoorganotrophs (fermenters)

• Clostridia - spore formers, Gram positive,
  bacilli, strict anaerobes. Serious diseases such
  as gangrene (Clostridium perfringens), botulism
  (C. botulinum), and tetanus (C. tetani)
• Lactic Acid - Gram positive organisms, produce
  lactic acid, catalase negative organisms Some are
  found in the mouth and the vagina and some found
  in milk and diary products. Two medically
  significant species are Listeria monocytogenes
  (listeriosis) and Erysipelothrix rhusiopathiae
  (erysipeloid). Also, Streptococcus,
  Enterococcus etc. can grow in oxygen environments
  but do not use O2 as a final electron acceptor.
  Medically important species include
  Streptococcus pyogenes (strep throat, rheumatic
  fever etc.), S. agalactiae (severe infections in
  newborns), and S. pneumoniae (otitis media,
  pneumonia, and meningitis)
• The genus, Propionibacterium, contains Gram
  bacilli some of which are important in the dairy
  industry

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Anoxygenic Phototrophs,probably the earliest
photosynthetic bacteria.

• Purple sulfur bacteria are large and are found in
  sulfur rich habitats but purple non-sulfur
  bacteria do not use sulfur.
• There are also green sulfur and non-sulfur
  bacteria.

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Oxygenic Phototrophs include the cyanobacteria.

• There are more than 60 genera.
• Some fix nitrogen, others oxidize hydrogen and
  others are nitrifiers.

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Aerobic Chemolithotrophs

• include the Sulfur oxidizing bacteria

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Aerobic Chemoorganotrophs

• Some are obligate aerobes
• Others are facultative anaerobes

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Obligate aerobes

• The pseudomonads - motile rods with polar
  flagella. Many produce pigments. Many are
  free-living, but some such as Pseudomonas
  aeruginosa, cause infections esp. in
  immunocompromised.
• Micrococci - Gram positive, spherically shaped
  bacteria, found on human skin, on dust, inanimate
  objects, and in soil. Micrococcus luteus
• Mycobacteria include harmless species and those
  that are medically important (e.g., Mycobacterium
  tuberculosis and M. leprae). They typically
  stain poorly with the Gram stain

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Facultative anaerobes

• Staphylococci - arranged in clusters, catalase
  positive. Staphylococcus aureus (sepsis, Toxic
  Shock Syndrome etc.).
• Enterobacteria - coliforms) or that are
  free-living. These organisms possess
  peritrichous flagella. Include many of medical
  significance Escherichia coli (normal flora but
  also meningitis, diarrhea, utis), Klebsiella
  pneumomiae (normal flora but also pneumonia),
  Proteus mirabilis (normal flora, utis), Serratia
  marcescens (normal flora, utis), Salmonella typhi
  (typhoid fever), S. typhimurium (food poisoning),
  Shigella dysenteriae (dysentery), and Yersinia
  pestis (plague).
• Corynebacterium - Gram bacilli. Some species
  are part of the normal flora, while there are
  some disease causing species e.g.,
  Corynebacterium diphtheriae.

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Miscellaneous bacteria

• Spirochetes -spirally shaped bacteria, flexible
  cell wall and axial filaments. Medically
  significant spirochetes include Treponema
  pallidum (syphilis), T. pertenue (yaws),
  Leptospira interrogans (leptospirosis), Borrelia
  recurrentis and B. hermisii (relapsing fever),
  and B. burgdorferi (Lyme disease).
• Curviform Gram - Bacteria include many
  saphrophytic species that live in aquatic
  habitats and bdellovibrios (which prey upon other
  species of bacteria). Medically significant
  curviform bacteria include Campylobacter jejuni
  (bacterial gastroenteritis), and Spirilium minus
  (rat bite fever).
• Vibrios - curved or straight Gram bacteria.
  Some are luminescent. The medically significant
  vibrios include Vibrio cholerae and V.
  parahaemolyticus.
• Rickettsias small, generally unable to
  reproduce outside of their hosts cells. The
  rickettsias are responsible for such diseases as
  Rocky Mountain Spotted Fever (Rickettsia
  rickettsia) and Q disease (Coxiella burnetii).
• Chlamydias - lack peptidoglycan, two forms in
  their life cycle.Medically significant species
  include Chlamydia trachomatis (the causative
  organism of a very common STD).
• Mycoplasmas - a diverse group of bacteria that
  are grouped together because they all lack cell
  walls. Some species are free living while others
  cause disease in both plants and animals (e.g.,
  Mycoplasm pneumoniae)

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Clostridium
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Yersinia pestis
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Luminescent bacteria
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Cyanobacteria
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Rickettsia
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Vibrio
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Mycoplasma
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• DOMAIN EUKARYA

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• KINGDOM PROTISTA

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Algae

• Many of the algae have a beneficial effect on
  humans and other organisms (e.g.,
  photosynthesis).
• Some algae do produce toxins that cause problems
  in marine ecosystems (paralytic shellfish
  poisoning). Red tides can result from large
  numbers of the dinoflagellate, Gymnodinium breve
  or be caused by Gonyaulax (more serious).
  Pfisteria piscida is a protist that causes high
  mortality in fish and also serious skin and
  neurological problems in other vertebrates
  (including humans).

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Gymnodinium breve
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Pfisteria
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Other protists

• Mastigophora posses one or more flagella. Some
  species are free living and many are live
  symbiotically with other organisms (e.g.,
  Trichonympha ). Medically significant
  flagellates include Trypanosoma sps. (Chagas
  disease and sleeping sickness), and Giardia
  lamblia (Hikers diarrhea).
• Ciliata possess cilia. Examples include
  Paramecium (a free living species) and one
  parasite, Balantidium coli.
• Sarcodina move by cytoplasmic streaming which
  results in amoeboid movement. Medically
  significant examples include Entamoeba
  histolytica (Travelers diarrhea) and Naegleria
  fowleri (encephalitis).
• Sporozoans are non-motile and form spores.
  Examples include Plasmodium sps. (malaria) and
  Toxoplasma gondii (toxoplasmosis)

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Naegleria
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Toxoplasma
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Giardia
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• KINGDOM MYCETEAE

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Fungi

• Many fungi are saphrophytic and play an important
  role in nutrient cycling.
• Many species cause disease in plants (e.g., Dutch
  elm disease) and a few species cause disease in
  humans.
• Some species are single-celled organisms (e.g.,
  yeasts).
• Filamentous forms are molds.
• Many of the fungi that cause disease in humans
  are opportunistic (e.g., Candida, Cryptococcus
  neoformans etc.) but a few species (four) are
  true pathogens (e.g., Histoplasma capsulatum).
• Some species of fungi are also involved in
  allergies and others are responsible for various
  skin infections (mycoses).

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Candida
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Athletes foot
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Histoplasma
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• KINGDOM ANIMALIAE

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Animals

• Animals that are included in microbiology or
  parasitology include
• The helminth worms e.g., Ascaris lumbricoides,
  Trichinella , Dracunculus medinensis , and
  Wucheria bancrofti
• The flukes e.g., Schistosoma (blood fluke) and
  the Oriental liver fluke, Clonorchis sinensis
• The other flatworms or tapeworms (e.g., Taenia
  saginata and T. solium)

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Dracunculus
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Ascaris
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Schistosoma
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Taenia
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• Viruses

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The stages of viral infection are

• 1. Attachment to the hosts cells
• 2. Penetration of the host cell (injection of
  the nucleic acid core)
• 3. Synthesis of nucleic acid and capsids
• 4. Assembly of new viruses
• 5. Lysis of the host cell with release of the
  viruses

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Emerging viruses include

• Ebola
• Hantavirus
• Marburg
• SSARs virus

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Prions diseases include

• BSE, Kuru etc.

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• End of notes for Exam II