Introduction to bacteria: Bacteriology Lecture 4 13/9/2015.

Introduction to bacteria: Bacteriology

Lecture 4 13/9/2015

Kingdom of bacteria

1. Sub-kingdom: Eubacteria

2. Sub-kingdom: Cyanobacteria

NomenclatureBinomial (scientific) nomenclature

Genus – always capitalizedspecies -, lowercaseBoth italicized or underlined: Saccharomyces cerevisiae or Saccharomyces cerevisiae

Staphylococcus aureus or Staphylococcus aureus

Staphylococcus epidermidis or Staphylococcus epidermidis

Escherichia coli or Escherichia coli

Distribution of bacteria

Live everywhere.

- water (fresh and salty),

- soil and air.

- Some of them can survive in ice and others can live in hot water. these can

form spores which are very resistant to drought , chemical , rays and

temperature variations.

- Some types live as saprophytes,

- while other are (Obligate or Facultative) parasites on plants, animals and

humans causing diseases.

Shapes and arrangement of bacteria

1- Coccus……… Cocci (spherical shape)

Depends on cell division their cell arrangements:

• Diplococci

• Streptococci (chain)

• Staphylococci (cluster)

• Sarcinia

2- Bacillus…….. Bacilli (rod-shaped bacteria)

According to their arrangement: it is divided to

• Diplobaccilli

• Streptobacilli (chain)

3- Coccobacili

4- Spiral shaped bacteria:

They can be divided into:

– Vibrion (curved) a comma shape

– Spirillia Coiled forms exhibiting twists with one or more turns. They have constant shapes and they move by flagella.

– Spirochaets They are intermediate between bacteria and protozoa, they don’t have cell wall and flagella. Their movement are like a worm.

5- Filamentous (Actinomycetes/Mold-like bacteria)

Their body consists of mycelium just like fungi. Streptomyces group belongs to these mold like bacteria. Streptomycin, an antibiotic is produced by Streptomyces.

General morphology of bacterial colony plays an

important role in microbial identification:

Round

Irregular

Flat

Convex

Domed

Motility (Movement)

• Bacteria are either non-motile or motile. Motile forms are either creeping or swimming:

• Creeping bacteria (e.g. Myobacterium) move or creep slowly on a supporting surface as a result of wave-like contractions (contract and relax) of their bodies.

• Swimming bacteria move freely in a liquid medium due to the presence of flagella. Flagellated forms differ with respect to number and pattern of attachment of flagella. The following forms:

1. Monotrichous. One flagellum attached to one pole of the cell.

2. Lophotrichous. A tuft of flagella at one pole of the cell.

3. Amphitrichous. A single or a tuft of flagella at the two poles of the cell.

4. Peritrichous. Many flagella distributed over the whole surface of the cell.

Arrangement basis for classification