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1.1	 Light microscopy uses visible light and a system of lenses to observe tiny objects which are naked to the human eye through magnification. Specimens viewed with a light microscope can either be living or dead but are usually stained with a well colored dye to make them visible under the light microscope. A light microscope also uses several lenses to obtain high resolution through the application of the best magnification. Light microscopy however does not provide enough resolution to view the organelles of the cell, on the contrary it only has resolution which allows us to only view the cell in general. There are several vital steps and precautions which have to be practiced when using light microscopy. Slides used in light microscopy have to be prepared using a very specific procedure and it has the following steps: •	Fixation which prevents distortion of the specimen •	Dehydration to prevent deflection of the electrons which blurs the image •	Embedding to support the tissue in wax •	Staining in order to increase the contrast between structures •	Mounting of slides to protect the specimen which provides suitable viewing

1.2	Bacterial cell walls are the only cell walls with the presence of a peptidoglycan. They withstand turgor pressure and maintains cell shape. In addition to that they also provide structural integrity to the cell and provides rigidity to the cell. Cell walls in bacteria could either be gram positive or gram negative. The gram positive bacterial cell walls are made up of 90% peptidoglycan layer and the gram negative only consists of a very minute fraction of the peptidoglycan. In the gram positive bacterial cell wall, the peptidoglycan is a very large polymer of interlocking chains of identical peptidoglycan monomers. Gram negative cell walls are thin and contains a very thin layer of peptidoglycan adjacent to the cell membrane.

1.3	Eukaryotic cell organelles – eukaryotic cells have membrane bound organelles which makes them very much advanced and complex cells. These cell organelles are more specialised units of the cell, enclosed in their own specific lipid bilayers, which allows them to perform various specific functions vital for the cell’s functioning and survival. The cells organelles in the eukaryotic cells are pretty much like to cells as the body organs such as the eye, heart etc. are to the body. They are of most importance. They are the building blocks of a eukaryotic cell and most of these organelles are not present in the prokaryotic cells. Some of the eukaryotic cell organelles are DNA containing and have originated from formerly autonomic microscopic organisms acquired through the process of endosymbiosis. On the contrary some of the eukaryotic cell organelles do not have their own DNA but still have endosymbiosis origins. Some of the well-known organelles of the eukaryotic cells are the mitochondria, chloroplasts Golgi apparatus, lysosomes etc. these organelles are partitioned which permits various kinds of biochemical reactions to occur in various organelles of the cell. They also perform uniquely specific functions but they also all work together in an integrated fashion to meet the eukaryotic cell’s needs. The nucleus is the well most important of the eukaryotic cell organelles because it localises the DNA and controls all the cell’s activities.

1.4	Nutrient uptake by bacteria – there are several forms which bacteria uses for the uptake of vital body nutrients. These vary from consuming dead/decomposed matter to autotroph bacteria which produces its own food using the solar energy, to mention but a few. Bacteria that consume dead matter usually first decompose e.g. leaves, cadavers etc. by secreting digestive enzymes in their skin onto the food source. Cyanobacteria for instance can photosynthesis during their synthesis of oxygen which we use, purple nonsulfure bacteria obtains its energy and nutrients from organic compounds. In so doing these mentioned bacteria are able to produce their own food and obtain nutrients from organic compounds, respectively. Some bacteria are symbiotic, thus they form a mutualistic benefit with other organisms i.e. humans and aid us in assimilating the food we consume at the same time also obtaining their much desired nutrients from our bodies without causing harm. Some bacteria actually manufacture essential nutrients which we cannot make on our own and in return they also obtain the nutrients they require from our bodies.

1.5	Bacteria growth curve – This is a graphical curve that shows the changes in the size of a bacterial population over time in a culture. Bacterial growth is a process characterised by asexual reproduction through a process known as binary fission and this can be purely achieved from culture media growth. The bacteria are cultured in sterile nutrient medium and incubated at optimum temperature for growth. Samples are continuously removed at intervals and the populations of viable bacteria is counted. Bacteria are also characterised by high rates of metabolism and sensitivity to antibiotics. A logarithmic curve is constructed is constructed from the data representing the population over time. The bacterial growth curve has four essential phases which begins with: •	The lag phase – bacteria are still adopting themselves to growth conditions. Individual bacteria still undergoes maturity and are not able to undergo cell division at this point in time. The cells are metabolically active and only their size not the populations increase. This period is intense since it involves a variety of physiological adjustments. •	Exponential phase – have developed prone to their environment. Their mass and size begin to increase in an exponential manner. An increase in cell size and an increase in metabolic rates start to occur. It is also characterised by the rapid growth and the division of colony cells through binary fission at a constant rate that is directly proportional to a much quicker growth rate. Cell doubling also occurs. The number of bacteria appearing per unit time is directly proportional to the present population and when growth issue is limited doubling continues at a constant rate. •	Stationary phase – this is also known as the growth limiting phase and one major factor that causes it is limited resources i.e. nutritional exhaustion etc. This is also a result of the growth rate being equal or in equilibrium with the dearth rate. The complete consumption of nutrients results in accumulation of waste material, toxic metabolites and inhibitory compounds i.e. antibiotics developing in the medium. Uncontrolled conditions such as pH, temperature etc. are also unfavourable for bacterial growth and lead to the bacterial populations decreasing. •	Death phase – dearth of bacteria occurs due to a complete depletion of nutrients, unfavourable conditions developing, autolysis of enzymes and accumulation of waste and consumption toxic material in the medium. Death is rapid at a very uniform rate as the populations of dead cells becomes more than the numbers of living cells.

1.6	Pasteurisation – this is a process invented by a French chemist, Luis Pasteur between 1822 and 1895. It involves the purification of foods at an optimum temperature that destroys undesirable, harmful (conditions) microbes without killing them and without a major alteration on the actual food’s chemistry. It also limits the rate of fermentation which also permits the growth of bacteria. It is a process widely used in treating beer, wine, fruit juices, cheese, eggs etc. unlike the actual sterilisation process, pasteurisation is not intended in killing the microbes in the food but instead it aims to reduce the number of viable pathogens so they won’t cause any infections. Pasteurisation effectively slows down the spoilage caused by microbial growth and make the food safely consumable for humans.

1.7	Pure culture – is culture obtained from one species of a microorganism. Pure culture can be effectively isolated from a single cell of a population with the aid of a micromanipulator or a very thing capillary. A pure culture can also be successfully obtained from mixed culture by carefully transferring a small sample into a new sterile growth medium in a manner that disperses the individual cells across the medium’s surface. It can also be obtained by thinning the sample manifold before inoculating the new medium. When the cells multiply, each will be a clearly distinct colony which can possibly be used to inoculate more medium. Isolation of pure culture may also be achieved by providing a mixed inoculum with a medium favouring the growth conditions of only one organism to the exclusion of the others. The isolation of pure culture is very vital in the classification and study of the variability of microorganisms, in the preparation of enzymes, antibiotics, vitamins, steroid hormones and in the production of vaccines.

1.8	Photoautotrophs – these are organisms (bacteria) with the ability to synthesis their own food using inorganic substances, use CO2 as their main carbon source and light as an energy source. Photoautotrophs also feed themselves by consuming food molecules from their close surroundings. Energy obtained from sunlight, water and CO2 is converted into inorganic material which is to be consumed in the food making process. Some of the inorganic material is also converted into organic material for use in cellular functions i.e. biosynthesis and respiration processes. Most photoautotrophs have the absence of a pigment which allows them to trap sunlight and convert the light energy into chemical energy. Since these organisms photosynthesis, they also provide nutrients for most life forms except for chemotrophs and autotrophs.

Question 2

Pilus/ pili Hair like structure on the surface of the prokaryotes cells which attaches to other bacterial cells. It performs the transfer of DNA from cell to cell, facilitates in cell motility, and adhering to solid surfaces.

Plasmalemma /cell membrane The cell membrane is constructed from lipids such as fats and proteins, some of which are also involved in the transport of substances in and out of the cell. It provides protection, holds the prokaryotic cell and its contents in the rightful positions, protects the cell from its surroundings, and provides a selective permeability which allows the transfer of various substances in and out of the cell. It also plays a role in ion conductivity. Its permeability is affected by polarity, charge and size of the particles involved.

Cell wall The cell wall is a strong, soluble and rigid semi - permeable protective layer of polysaccharides outside the Plasmalemma/ cell membrane. It provides the cell with tensile strength, rigidity and maintains its structure. Its semi – permeability also filters substances in and out of the cell.it also protects the cell from mechanical stress and infections from the cell’s surroundings. In addition to that it provides the cell with limited plasticity which prevents the cell from rupturing due to turgor pressure. Its composition differs from species to species and in prokaryotes it is made up of peptidoglycans.

Capsule It is a very large polysaccharide structure that is positioned outside the cell envelop/ the cell membrane of a prokaryotic cell wall. The type of capsule found in prokaryote bacteria is glycocalyx which is a thin layer of tangled polysaccharide fibres which occurs on most surfaces of cells growing in nature. It is a well-designed layer, not easily washed off and it can also be the cause of various diseases. In bacteria capsule can be found in both gram positive and gram negative. The capsule protects bacteria (prokaryotes) cells from engulfment from attack by antimicrobial agents. In certain soil bacteria they protect cells from perennial effects of drying. Capsule material could also be overproduced from sugars in bacteria, later transformed and stored as reserve of carbohydrates for metabolism process.

Cytoplasm The cytoplasm is a clear liquid found in between the cell membrane and the nucleus of a cell. It is a gel – like structure composed mainly of water and contains enzymes, salts, organelles and many other molecules. It allows the movement of organelles and materials around the cell through cytoplasmic streaming. It is also referred to as cytosol, which means substance of the cell. It serves as a molecular soup as all the organelles are suspended in the cytoplasm. It also helps to dissolve waste products.

Ribosomes Are tiny substances consisting of RNA and are associated proteins found in large numbers free in the cytoplasm of (prokaryotes) cells. Ribosomes make up about 30% of the prokaryotic cell mass and are synthesised in the cytoplasm of the prokaryotic cells and aren’t entirely organelles. They are composed of the smaller subunit, which functions in the association with mRNA during translation and decoding, the bigger subunit which functions as a peptyl transferase centre as well as the sight of peptide bond formation. These subunits join catalyse the translation of mRNA into polypeptides chain during protein synthesis. Ribosomes are involved in the synthesis of peptides proteins and polypeptides. They also translate genetic material from mRNA into proteins during DNA translation.

Nucleoid region The nucleoid region is not a true nucleus but it’s very much nuclear - like. It is only found in the prokaryotic cells and it is identified by its irregular circle - like shape and it lacks the presence of a nuclear sac or a nuclear membrane around it. The nucleus localises the genetic information (DNA) of the prokaryotic cell. This DNA is not housed by a nuclear membrane due to its absence. DNA found in the nucleoid region is circular and its copies could multiply at any given instant. The nucleoid region has all the genome of a prokaryotic cell since it houses all the necessary genes vital for growth of an organism and its survival. Since prokaryotic ribosomes aren’t separated from the nucleoid region, they bind to the mRNA being produced and begin making proteins. In turn this phenomenon makes the nucleoid region a site for protein synthesis as well.

Mesosme These are unusual structures produced by the chemical fixation techniques used to prepare electron microscope sample. They are only common to prokaryotic bacterial cells and usually identified as convulted invagination. Mesosomes function in the excretion of exoenzymes, binary fission and during the DNA replication of prokaryotic cells. These also function as sites for of localization of respiratory enzymes in addition to their involvement to secretion of glycocalyx as well as their ability to increase the surface area of the cell membrane.

Flagella It is a very tiny thread – like structure made up of protein and a molecule: flagellin. Cells (prokaryotic cells) can have one or more flagella. Their basic is to assist in locomotion of the cell which is a process achieved by the flagellum’s continuous rotation. Flagella also has a neuroma function as it is also allows signal transduction and sensation through their rotation and movement.

Question 3.1

Microbial growth in a closed system - Batch is a closed system characterised by four distinct phases i.e. lag, exponential, stationary and death phase. In a closed system, all material are added to the system at the beginning of the process and no additional nutrients are added. Since the system is closed, waste material are not removed until the end of the process. Products are only removed when the process is finished and the results shows the distinct characteristics of a growth curve.

Microbial growth in an open system is characterised by the addition of nutrients continuously during the process. Wastes can also be removed continuously even during the process to try and maintain continuous growth. Products can also leave the process at any time during or even after the process. An open cultivated system also maintains a steady state condition, in which the rate of increase of cell biomass with time is equal to zero, the total number of cells are constant and the total volume in the bioreactor are constant.

Environmental – nutrients: nutrients in the growth medium should provide all the vital elements necessary for the successful growth of bacteria and the synthesis of new organisms. Carbon, Hydrogen, Nitrogen, Sulphur, Phosphorous Mineral sources and Trace elements must be provided by the medium. Growth – organic compounds needs to be available in order for the bacterial cells to successfully grow. Bacterial cells cannot break organic substance therefore they need to be supplied in the form of nutrients in order for the cells to successfully consume the organic matter. Metabolites – these are significant for the frequent and effective growth of bacterial cells and in order for them to be easily produced by the bacterial cells, they need to be provided in the medium The medium pH – the right amount of pH for optimum growth needs to be obtained in the medium for the effective growth of bacterial cells. Temperature – optimum temperature which is favourable for the growth of most types of bacterial cells Light/darkness – optimum amount of light to darkness depending on whether the bacterium favours light or darkness for growth despite most bacteria being favourable to darkness. Source of metabolic energy – either fermentation, respiration or photosynthesis has to be used by the various forms of bacteria in order to generate metabolic energy.