LIVING CELL

MICROBIAL CELL microorganisms have been used by humans

since prehistoric times in the preparation of food, alcoholic beverages, milk products etc

the role of microorganisms in biotransformation was recognized 19th century

Today, they are not only used for the traditional microbial processes but also for new processes such as the production of pharmaceuticals, industrial chemicals, enzymes, agricultural chemicals, waste water treatments, etc

Microbial cell

The protists simple biological organisms compared to plants and animals; algae, protozoa, fungi, and bacteria

unit structure of all living organisms: prokaryotes and eukaryotes.

Prokaryotic cell unit of structure in two microbial groups: bacteria

and blue-green algae. small and simple the cell is not compartmentalized by unit membrane

systems. has only two structurally regions: i) cytoplasm and ii)

nuclear region (or nucleoplasm). The cytoplasm has grainy dark spots content of

ribosomes, which are composed of protein and ribonucleic acid (RNA).

The ribosome the site of important biochemical reactions for protein synthesis.

The nuclear region is of irregular shape, sharply segregated even though it is not bounded by membrane.

The nuclear region contains deoxyribonucleic acid (DNA), which contains genetic information that determines the production of proteins and other cellular substances and structures.

The prokaryotic cell is surrounded with a cell wall and a cell membrane.

The cell wall, considerably thicker than the cell membrane, protects the cell from external influences.

The cell membrane (or cytoplasmic membrane) is a selective barrier between the interior of the cell and the external environment.

The cell membrane serves as the surface onto which other cell substances attach and upon which many important cell functions take place.

Eucaryotic cell unit structure in plants, animals, protozoa, fungi, and

algae cell has internal unit membrane systems that

segregate many of the functional components of the cell

1,000 to 10,000 times larger and more complex than prokaryotic cells.

The nucleus is surrounded by a double membrane with pores 40 to 70 mµ wide, containing cytologically distinguishable chromosomes.

The nucleus controls hereditary properties and all vital activities of the cell.

The chromosomes are long and threadlike bodies and are found in the nuclei of cells, which contain the genes arranged in linear sequence in nucleoproteins (proteins plus nucleic acid).

The cytoplasm contains large numbers of granules called ribosome, which are involved in continuous reactions to synthesize cell materials.

The ribosome is especially concentrated along the rough surface of the endoplasmic reticulum, an irregular network of interconnected membrane-delimited channels.

The mitochondria contain the electron transport enzymes that utilize oxygen in the process of energy generation.

Vacuole and lysosome are organelles that serve to isolate various chemical reactions in a cell.

Microbial nomenclature binomial system each organism has two name

parts Proper names of organisms are always italicized The first word is the name of the genus (plural,

genera) in Latin or Greek word and is capitalized The second word is the species name and is not

capitalized There may be several species with the same

genus name E.g: Lactobacillus plantarum. L. acidophillus, L.

casei

Bacteria

Unicellular, about 1500 species Diameter 0.5 to 1m, vary greatly in length Shape: cocci (spherical/ovoid), bacilly (cylindrical/rod),

spirilla (helically coiled)

• Reproduction: asexual binary fission

• reproduction steps: 1)cell elongation, 2)invagination of the cell wall, 3)distribution of nuclear

material, 4)formation of the transverse

cell wall,5)distribution of cellular

material into two cells, an6)separation into two new

cells

Elemental composition

Physical conditions for bacteria 3 major physical factors: T, gaseous environment, and pH microbial activity and growth manifestations of enzymatic

action the rates of enzyme reactions increase with increasing T;

the rate of microbial growth is T dependent the optimum pH for bacteris growth lies: 6.5 - 7.5. Although a few bacteria can grow at the extremes of the pH

range, the limits fall somewhere between pH 4 and pH9.

The principal gases in the cultivation of bacteria are O2 and CO2

There are four types of bacteria, according to their response to oxygen:1. Aerobic bacteria grow in the presence of free O2.2. Anaerobic bacteria grow in the absence of free O23. Facultatively anaerobic bacteria grow in either the absence or the presence of free oxygen.4. Microaerophilic bacteria grow in the presence of minute quantities of free oxygen

Some bacteria form spores when growth ceases due to starvation or other causes

Spores are more resistant than normal cells to heat, drying, radiation, and chemicals.

Spores can remain alive for many years; however, they can convert back to normal cells at proper conditions

FUNGI

Plant devoid of chlorophyll unable to synthesize their own foods

range in size and shape from single-celled yeasts to multicellullar mushrooms

YEAST & MOLD

Yeast widely distributed in nature (food, soil, in

the air, on the skin and in the intestines of animals)

depend on higher plants and animals for their energy

Unicellular spherical to ovoid Size: 1 to 5 m in width; 5 to 30 rn in

length The cell wall quite thin in young cells but

thickens with age.

Asexual reproduction BUDDING

A small bud (or daughter cell) is formed on the surface of a mature cell. The bud grows and is filled with nuclear and cytoplasmic material from the parent cell. When the bud is as large as the parent, nuclear apparatus in both cells is reoriented and the cells are separated. The daughter cell may cling to the parent cell, often even after the cells are divided

Saccharomeces cerevisiae wine, beer, leavening of bread

Mold filamentous fungi A single cell or spore (conidia) is germinated to form a

long thread, hyphae, which branches repeatedly as it elongates to form a vegetative structure called a mycelium. Since a mycelium is capable of growing indefinitely, it can attain macroscopic dimensions.

Find everywhere Aspergillus,

penicillium, rhizopus

used in the production of antibiotics, enzymes, food and food additives

Animal cell Eukaryotic cells They are bound together by intercellular material to

form tissue Tissue is customarily divided into four categories:

epithelium, connective tissue, muscle, and nerve

Epithelial tissue forms the covering or lining of all free body surfaces, both external and internal.

Connective tissue, the cells are always embedded in an extensive intercellular matrix, which may be liquid, semisolid, or solid

Muscle cells are usually bound together into sheets or bundles by connective tissue are responsible for most movement in higher animals

Nerve cells are composed of a cell body, containing the nucleus and fibers. easy to be stimulated

PlantCell The size within the range of 20-40 mm in diameter and

100200 mm long Structure typical eukaryotic cells However, plant cells have distinctive features such as

a rigid wall, a large vacuole, and the presence of chloroplasts

Chloroplast is the site of photosynthesis in the plant cell, which contains the green pigment chlorophill that is responsible for trapping the light for the production of carbohydrates

The plant cell is surrounded by a cell wall The outer layer of the cell wall serves as the glue to

hold one plant cell firmly to an adjacent cell. The inner layer of the wall is cell membrane

completely different from the cell wall in form, composition, and function.

the wall i a rigid, relatively thick structure, carbohydrate in nature, provides support

the cytoplasmic membrane thin (approximately 75 A) and flexible, composed of protein and lipid, regulates the movement of substances into and out of the cell.

The vacuole serves as a receptacle for waste metabolic products or secondary plant substances. The vacuole is surrounded by a plasma membrane. The major component of large vacuoles is water, which contains dissolved solutes, such as inorganic ions, amino acids, organic acids, water-soluble pigments and insoluble materials in the form of crystals and needles.

In addition, the vacuole also contains proteins such as hydrolases, catalase, and phosphatases.

differences between plant & microbial cells:

1. Plant cells are 10 to 100 times larger than bacterial and fungal cells (20-40 m in diameter and 100-200 m long)

2. The metabolism of plant cells is slower than microbial cells the maintenance of sterility for a longer period of time.

3. Plant cells tend to grow in clumps which cause sedimentation, poor mixing, plugging the inlet and outlet lines, wall growth, and so on.

4. Plant cells are more sensitive to shear than microbial cells.

5. Metabolic production in plant cells is subject to more complex regulatory mechanisms than metabolic production in microbial cells.

6. Plant cells are more genetically unstable than microbial cells.

Differences between plant and animal cell:

Energy

for supporting biosynthesis activities (e.g. growth, work)

Source of energy: C & light

Grouping organism according to energy pathway: autothophic & heterotrophic

Autotrophic organism that produces complex

organic compounds (such as carbohydrates, fats, proteins, cell wall etc) from inorganic raw material including CO2 as principal/carbonates/simples inorganic compounds (e.g. ammonium sulfate, magnesium sulfate and sodium chloride) by using basic energy sources such as sunlight

Subdivided on the basis of their ability to utilize the energy for cell growth: phototrophs and chemotrophs

Phototrophs use light as an energy source (e.g. plants)

Chemotrophs from inorganic sources (H2S, CH4, CO2). e.g bacteria lives in waste water, volcanoes, deep sea ocean vents, the atmosphere, mines)

Heterotrophic use organic compounds as a source of energy and

organic material for synthesis of cellular components.

1. photoautotropic: light as energy source, CO2 as C source (higher plants)

2. Photoheterotrophic: light as energy source, organic comp. as C source

3. Chemoautotropic: chemical as energy source, CO2 as C source; have ability to use reduced inorganic comp as oxidizable energy sources (NH3, NO2, H2S etc)

4. Chemoheterotrophic: chemical as energy source, organic comp. as C source (fungi, great number of bacteria)