Diversity Of Microorganisms 1- Prokaryotic

PART 1 Prokaryotic Microbes

Contains

23 phyla, 32 classes, 5 subclasses, 77 orders, 14 suborders, 182 families, 871 genera, and 5,007 species. Phenotypic categories • Gram-negative and have cell wall • Gram-positive and have cell wall • Lack cell wall.

 Cell

morphology  Staining reactions  Motility  Colony morphology  Atmospheric requirements  Nutritional requirements  Biochemical and metabolic activities  Specific enzymes that the organism produces  Pathogenecity  Genetic composition

Shapes and Arrangements of Bacteria (Separate Presentation)

Bacteria

can lose their characteristic shape because of adverse growth condition which prevents the production of normal cell wall. Some can revert back to normal shape while others cannot. Mycoplasma do not have cell walls. Pleomorphism- ability to exist in variety of shapes.

Mycoplasma pneumoniae

Preparation

of smear Heat fixation Methanol fixation Purpose of fixation: • Kills the organism • Preserves their morphology • Anchors the smear to the slide

Simple

staining

• Determine the morphology • Dye is applied to the fixed smear, rinse, dried and

examined using OIO. Structural

staining

• Use to observe bacterial capsules, spores, and

flagella. Differential

staining

• Gram staining • Acid-fast staining

Gram-positive & Gram-negative

Difference between Gram-positive and Gram-negative Bacteria Gram Positive Gram Negative Color Peptidoglycan Teichoic acids and lipoteichoic acids in cell walls Lipopolysaccharide in cell walls

Blue-to-purple

Pink-to-red

Thick layer

Thin layer

Present

Absent

Absent

Present

Clostridium tetani

Bacillus subtilis

Gram-positive bacteria tend to be killed by penicillin and detergents. Gram-negative bacteria are more resistant to antibiotics.

Use

to identify Mycobacteria spp. Carbol fuschin (bright red) is driven into the bacterial cell using heat. Heat softens the waxes of the cell walls of Mycobacteria, enabling the stain to penetrate. A decolorizing agent (acid-alcohol) is then used in an attempt to remove the red color from the cells.

Because

Mycobacteria are not decolorized by the acid-alcohol, they are said to be acid-fast. Most bacteria are non acid-fast. Acid-fast stain is especially used in TB labs. Developed in 1882 by Paul Ehlrich.

Acid-fast staining: Mycobacterium leprae

Negative

staining is useful for capsules. Endospores staining- heat is required to drive a stain into endospores. Flagella staining requires a mordant to make the flagella wide enough to see.

Motile

and nonmotile Presence of flagella, axial filaments or capable of gliding motility.

Endoflagella In

spirochetes Anchored at one end of a cell Rotation causes cell to move

Bacterial

colony- mound or pile of bacteria in a solid culture medium. Contains million of organisms. Colony morphology varies from one species to another. • Size • Color • Over-all shape • Elevation • Margin

Oxygen

Obligate aerobes

(O2)

Facultative anaerobes

Obligate anaerobes

Aerotolerant anaerobes

Microaerophiles

CO

2

- Canophiles

Nitrogen

• • • •

In amino acids, proteins Most bacteria decompose proteins Some bacteria use NH4+ or NO3− A few bacteria use N2 in nitrogen fixation

Sulfur

• In amino acids, thiamine, biotin • Most bacteria decompose proteins • Some bacteria use SO42− or H2S

Phosphorus

• In DNA, RNA, ATP, and membranes • PO43− is a source of phosphorus

Organic

Growth Factors

• Organic compounds obtained from the

environment • Vitamins, amino acids, purines, pyrimidines Carbon

• Structural organic molecules, energy source • Chemoheterotrophs use organic carbon sources • Autotrophs use CO2 Trace

Elements

• Inorganic elements required in small amounts • Usually as enzyme cofactors

Capsules Pili Endotoxins Exotoxins Exoenzymes

Nuclear

area (nucleoid)

Obligate

intracellular parasites:

• Ehrlichia and Anaplasma spp. Tick-borne,

ehrlichiosis • Rickettsia. Arthropod-borne, spotted fevers R. prowazekii Epidemic typhus R. typhi Endemic murine typhus R. rickettsii Rocky Mountain Spotted Fever

Human

pathogens:

• Bartonella • B. hensela • Coxiella

milk

Trench fever Cat-scratch disease Q fever transmitted via aerosols or

 Chlamydia  Energy

parasites  Mode of transmission: inhalation of aerosols or direct contact between hosts  C. trachomatis • Trachoma • STD, urethritis  C.

pneumoniae  C. psittaci • Causes psittacosis

 Mycoplasma  Wall-less,

pleomorphic  0.1 - 0.24 µm  M. pneumoniae  Pleuropneumonia-like organsims (PPLO)  Tiny colonies (fried egg colonies)  Resistant to antibiotics

Thiomargarita

namibiensis- largest bacteria (750 µm) Epulopiscium fishelsonii- another enormous bacteria (80 µm X 600 µm) Nanobacteria- less than 1 µm, found in soil, minerals, ocean water, dental plaque, and even rocks (meteorites)

Thiomargarita namibiensis

Epulopiscium fishelsonii

Nanobacteria

Includes

purple bacteria, green bacteria and cyanobacteria. Oxygenic photosynthesis Anoxygenic photosynthesis 2H2O + CO2

2H2S + CO2

light

light

(CH2O) + H2O + O2

(CH2O) + H2O + 2S0

Cyanobacteria

purple sulfur bacteria

green sulfur bacteria

Discovered

in 1977 Genetic contains 2 phyla, 8 classes, 12 orders, 21 families, 69 genera, and 217 species. Genetically, archaeans are closely related to eukaryotes than bacteria.

Thermophiles  Heat-loving

archaebacteria found near hydrothermal vents and hot springs  Many thermophiles are chemosynthetic using dissolved sulfur or other elements as their energy source and iron as a means of respiration

Halophiles  Thrive

in unusually salty habitats. Some can thrive in water that’s 9% salt; sea water contains only 0.9% salt.  Have light-sensitive pigment bacteriorhopsodin which absorbs energy from sunlight  Example: Salt Lake and Dead Sea

Psychrophiles like

extremely cold temperatures (even down to -10 degrees Celsius). Live in arctic and antartic oceans

Methanogens  are

anaerobic archaebacteria that produce methane  are found in sewage treatment plants, bogs, and the intestinal tracts of ruminants.  ancient methanogens are the source of natural gas.

Next topic: Part 2 Eukaryotic Microbes