Micro organismsMicro-organisms

• Study of organisms too• Study of organisms too small to be clearly seen by the unaided eye (i.e., micro-organisms)

• Size < ~1 mm (microscopic organisms)

• Mainly single-celled organisms

• Lack organs and true tissue

• Some multi-celled organisms have primitive tissues

V h t• Very heterogeneous group

Micro organismsMicro-organismsCan be divided into:

Procaryotes (lack a true membrane-delimited nucleus)

1. archaea or archaeobacteria2. bacteria or eubacteria

--------------------------------Eucaryotes (have a membrane-enclosed nucleus, are more complex morphologically and aremorphologically and are usually larger than procaryotic cells)

3 algae Eukaryotes have organelles!3. algae4. fungi5. protozoa

--------------------------------

6. viruses (obligate parasites)

Examples of the importance of micro-organisms

• The oldest and most common form of• The oldest and most common form of life

• Mineralization (biogeochemical c cles bioremediation compostingcycles, bioremediation, composting, water purification, etc.)

• Useful to macro-organisms (nitrogen fi i i i bi i lfixation, nutrition, symbiosis, normal flora, photosynthesis etc.)

• Biotechnical processes (food,

Fossilized bacteria

p ( ,pharmaceuticals, chemical products, etc.)

• Pathogenic micro-organismsPathogenic micro organisms (infectious diseases, product spoilage, etc.)

• Model systems in biology (genetics• Model systems in biology (genetics, physiology, metabolism, etc.)

The oldest and most common form of life

Earth4.5 billionyears old

3 5 billi3.5 billion

1.4 billion

The oldest and most common form of life

Mineralization (biogeochemical cycle, bio-remediation composting water purification etc )remediation, composting, water purification, etc.)

Useful to macro-organisms

Useful to macro-organisms

Biotechnical processes

Biotechnical processes

Pathogenic micro-organisms

Pathogenic micro-organismsPathogenic micro-organisms

The Nobel Prize in Medicine 2005

P th i i iPathogenic micro-organisms

Main morphological groups – Bacteria- size, appearance and cell arrangement

- two basic forms: cocci and bacilli

Bacilli or rods: CylindricalCocci: spherical cells 1 2 µm Bacilli or rods: Cylindricalshape, diam 1 µm, length2-5 µm

Cocci: spherical cells, ~1-2 µmin diam. Cell arrangement uponcell division:

- Coccobacilli: very shortbacilli, reminiscent of cocci

- Vibrions: a twisted

- Diplococci- Streptococci- Staphylococci

T t d Vibrions: a twistedbacillus, not a completespiral, 2-3 µm long

S i ill b illi l i id

- Tetrads- Sarcina

- Spirilla bacilli: long, rigid,spiral bacilli with flagellae,6-15 µm long

Exceptions

- Flat, quadratic bacteria:- Spirochet bacilli: long,flexible, spiral bacilli withan axial filament

, q0.25 x 2 x 2-4 µm

- Pleomorphic: no particular shape lack cell wall

- Hyphae that form a micelleshape, lack cell wall

Cocci: spherical cells, ~1-2 µm in diam.

Streptococcus pyogenes

Staphylococcus aureus

Bacilli or rods:Bacilli or rods:Cylindrical shape, diam 1 µm, length 2-5 µm

Escherichia coli Bacillus subtilis

Vibrions: a twisted bacillusVibrions: a twisted bacillus

Spirillaspiral bacilli with flagellae, 6-15 µm long

Spirochetspiral bacilli with an axial filament

Micelle-forming bacteriaMicelle-forming bacteria

The genus Streptomyces includes about 500 species.Constitutes 1-20% of the cultivable earth flora.Forms geosmin or earth smell and a large number of antibioticsForms geosmin, or earth smell, and a large number of antibiotics.

Bacterial staining methodsBacterial staining methods

• Aim:• Aim:To increase contrast in microscopy slides for the systematisation of bacteria

• Principle: - Basic (cationic) dyes, e.g. violet, methylene blue and malachite green

- Acidic (anionic) dyes, e.g. eosin and Congo red

- Fat-soluble dyes such as Sudan black

• Fixing: Heat or chemicals (formaldehyde, acetic acid or alcohol) are used to fix bacteria on slides in order to increase the penetration of the dye.

Bacterial staining methodsBacterial staining methods

G t i iGram staining: (Christian Gram, 1884)

• Heat fixing• Crystal violet

Lugol’s solution (KI + I )• Lugol s solution (KI + I2)• EtOH or acetone• Safranin (counterstain)

Gram-positive bacteria = blueGram-negative bacteria = redGram negative bacteria red