Principles of Biotechnology Lectures of week 4 MICROBIOLOGY AND BIOTECHNOLOGY
INTRODUCTION TO MICROBIOLOGY What are microbes? Germs, microbe s s microorganisms are minute living things that individually are too small to be seen with the unaided eye. The group includes: bacteria, fungi (yeast and mold), protozoa, microscopic algae, and viruses. Only a minority of microorganisms are pathogenic (disease producing).
A Bright-field microscope
A Transmission electron microscope (TEM)
Naming and classifying microorganisms Scientific nomenclature assigns each organism two names The genus (plural genera) is the first name and is always capitalized; The species: Specific epithet, not capitalized. e.g Bacillus (genus) thuringiensis (species) The organism is referred to by both the genus and the specific epithet, and both names are underlined or italicized.
Examples Bacillus thuringiensis, Bacillus thuringiensis Escherichia coli, Escherichia coli Scientific names can, among other things, describe an organism such as: A- honor of researcher B- or identify the habitat for species For Example :
Staphylococcus aureus a bacterium commonly found on human skin. Staphylo- describes the clustered arrangement of the cell, coccus,indicates that they are shaped like spheres, aureus, is Latin for golden, the color of many colonies of this bacterium. Escherichia coli: : is named for a scientist, Theodore Escherich, whereas its specific epithet, coli, indicates that it lives in the colon, Large intestine.
Types of Microorganisms Bacteria (prokaryotes): the majority among microorganisms. Archaea: : Live in extreme environment, the Methanogens, extreme halophiles,, and extreme thermophiles. Fungi: (singular: fungus) are eukaryotes organisms whose cells have a distinct nucleus containing the cell genetic materials, surrounded by a special envelop called the nuclear membrane. Fungi could be unicellular of multicellular.
TEM view of bacterial cells
Yeast cells
Protozoa (singular: protozoan). are unicellular, eukaryotic microbes. They move by psuedopods,, flagella, or cilia. Algae (singular: alga): are photosynthetic eukaryotes with a wide variety of shapes and both sexual and asexual reproductive forms. Viruses: are very different from the other microbial groups mentioned above. They are so small that most can be seen only with an electron microscope, and they are acellular (not cellular).
Herpesviruses
TEM herpes viruses
Comparison of a procaryotic and euocaryotic cells
Cheek cells (animal cell)
Brief History of Microbiology 1665 Robert Hook- First observation of cells, Hook was able to see individual cells (boxes). His discovery marked the beginning of the cell theory- the theory that all living things are composed of cells. 1637 Van leeuwenhoek- First observation of live microorganisms through magnifying lenses.
1735 Linnaeus- Nomenclature for organisms. 1857 Pasteur- Fermentation and pasteurization. 1876 Robert Koch Germ theory of Disease. 1923 Fleming- Penicillin / Griffith- Transformation in bacteria. 1941 - Beadle and Tatum- relationship between genes and enzymes.
Prokaryotic Cell Structure Size, shape, and arrangement Many bacteria are similar in morphology, there is remarkable amount of variation. Fig. 3.1 Shape of bacteria: 1. Coccus: : spherical cells. Diplococci e.g. Neiseria Streptococcui, entrococcus,, and lactococcus.. Divide in one plane Fig. 3.1b Staphylococcus: : divides in random planes to form grape like form Fig. 3.1a
2. Rod shape: bacillus e.g. Bacillus megatrium Fig.3.1c Long rod twisted into spiral or helices called spirella if rigid and spirochetes when flaxible: : Fig3.1d Curved Bacilla: Virbio Fig 3.1e 3. Multinucleate filaments or Hyphae E.g. Actinomycetes Fig 3.2a 4. Some bacteria ( unusual ) are variable in shape and lak a single characteristic form Fig 3.2b. These are called pleomorphic e.g. Corynebacterium.
Cell shapes in bacteria
Cells grouped together
Rod Shaped bacteria
Bacillus
Bacillus
Streptobacillus (chain)
Sallmonella typhimurium
E.coli
Spirillum-shaped
A sexual reproduction of bacteria (binary fission)
Size of bacteria Bacteria vary in size as much as in shape. The smallest about 0.3µm m in diameter e.g. genus Mycoplasma, approximately the size of poxiviruses Recently their have been reports of even smaller cells called Nanobacteria or ultramicrobacteria rang from 0.2 µm m to less than 0.05 µm m in diameter. Cyanobacterium oscillatoria is about 7 µm m in diameter as red blood cell. A large bacteria has been discovered e.g. Epulopiscium fishelsoni 600 by 80 µm.
Prokaryotic cell organization Cell wall is chemically complex and different in gram negative and gram positive bacteria. Genetic materials is located in a discrete region, the nucleoid,, No nuclear membrane.
Prokaryotic cell membrane To understand membrane function, it is necessary to become familiar with membrane structure and particularly with plasma membrane structure.
The plasma membrane Contain both proteins and lipids Lipids form bilayer in membrane.
Functions of plasma membrane 1. Retain the cytoplasm and separate it from the surroundings. 2. Serve as a selectively permeable barrier. 3. Location of a variety of crucial metabolic processes. 4. Contains special receptors that help bacteria detect and respond to chemicals.
Molecular Chaperones Special helper proteins aid the newly formed or nascent polypeptide in folding to its proper shape. These proteins recognize only unfolded polypeptide or partly denatured proteins and do not bind to native proteins Molecular chaperones suppress incorrect folding and may reverse incorrect folding that already take a place. Present in both prokaryotic and eukaryotic cells.
The Nucleoid No nuclear membrane in prokaryotes. Chromosome, a single circle of double- stranded deoxyribonuleic acid (DNA), is located in an irregularly shape region called nucleoid or chromatin body or nuclear region.
The prokaryotic cell wall It is very important for the following reasons: 1. Most bacteria have strong walls that give them shape and protect them. 2. The cell wall of many pathogens have components that contribute to their pathogenicity. 3. The wall can protect a cell from toxic substances and is the site of action of several antibiotics.
The prokaryotic cell wall - Gram positive bacteria cell wall Fig 3.19 - Gram negative cell wall is quite complex Fig 3.19 - A space is seen between the plasma membrane and the outer membrane in electron Micr.. Of G negative bacteria and some times a similar but smaller gap may be observed between plasma membrane and wall in gram positive bacteria. It is called Periplasmic space.