Unit -1

Metabolism – it refers to the sum of biochemical reactions taking place in a living organism, it couples both anabolism and catabolism.

Anabolism - Biosynthesis of macromolecules (e.g. polysaccharides and proteins) from monomers or metabolic pool of precursors (e.g. glucose, amino acids) during cell growth. e.g. peptidoglycan synthesis and CO2 fixation

Catabolism – Breakdown of large molecules or monomeric nutrients (e.g. glucose) to complete dissimilation (CO2) or formation of precursor’s molecules (pyruvic acid, oxaloacetate) that are used for biosynthesis, Catabolism culminates with release of energy (ATP) and reduced compounds (NADH2), produced by phosphorylation (Substrate level phosphorylation or Oxidative/Photophosphorylation) that are again used for biosynthesis. e.g. glucose break down by glycolysis-citric acid cycle.

Nutrition – is a process by which chemical substances called nutrients are transported into the cell from external environment and used in cellular activities such as metabolism and growth.

Nutrient – any substance required by an organism, whether in elemental or molecular form that must be provided to an organism is called nutrient. Once absorbed, nutrients are processed and transformed into the chemicals constituents (biomolecules) of the cell.

Microelement or Trace element or Micronutrient – They are required in smaller amounts (0.01- 1µM) than those of the Macroelements,   but essential for proper growth and development, they are involved in enzyme function and maintenance of protein structure. e.g. Zn, Ni and Cu.

Macronutrients – are required in relatively large quantities (mM to M quantities), primarily provide energy and play principal roles in building the cell structure and metabolism.  Examples of macronutrients are carbon, hydrogen, and oxygen present in macromolecules like carbohydrates and proteins.

Autotroph (auto - self; troph -  feed or nourish) – an organisms that can able to grow on atmospheric CO2 as a sole source of carbon, thus CO2 is assimilated into cell carbon. e.g. cyanobacteria and plants

Heterotroph (Hetero - other; troph - feed or nourish) – an organism that requires organic carbon as its carbon source. They are also called chemoorganotrophs. e.g. glucose and acetate are C sources used by E. coli and all fungi and humans.

Vitamins/growth factors – it is generic term describing broad range of unrelated organic compounds, many of which required in small quantities (0.1 to 1µM) for normal metabolism and growth of microbes. They typically functions as co-enzymes and most organisms synthesize their vitamin requirement. e.g. nicotinic acid (NADH2), riboflavin (FAD).

Psychrophile – organisms that grows at low temperature, mainly at 0˚C and has an optimum growth temperature of 15˚C or lower. e.g. Flavobacterium, Chlamydomonas nivalis and Psychromonas ingrahami (currently the lowest temp. surviving organism).

Mixotroph - An organism that uses organic compounds as carbon sources but uses inorganic compounds as electron donors for energy metabolism. e.g. Beggiatoa use acetate (as C source) and H2S (as energy).

Microaerophile – organisms that requires less levels (2-10%) of O2 for their growth and metabolism and the common level (20%) of O2 in the environment will damage the cells.  e.g. Campylobacter and Azospirillum.

Chemotrophs – refers to nutritional grouping of microorganisms based on the energy source they use during their growth, it has two sub types, one is chemoautotroph e.g. Acidithiobacillus sp., obtains energy from the inorganic chemical compounds (e.g. H2S) and the other is chemoorganotrophs e.g. E. coli and all fungi – obtains energy from the organic compounds (e.g. acetate and glucose).

Siderophores – They are low molecular weight (600-1500 daltons) high affinity iron (Fe3+) binding organic compounds synthesized and secreted out of the microbial cell, they aids iron nutrition in microbes.

Coenocytic - A term commonly used to denote the type of hypha produced by the fungi. 

A coenocyte is a multinucleate cell, lacks cross walls, it can result from multiple nuclear divisions without accompanying cell divisions, they don’t have a septa (cross walls), they are also called non septate. Thus coenocytic hypha is not compartmentalized. E.g. fungi belonging to the class Zygomycetes like Rhizopus sp. and Mucor ; hyphae having septa are referred as septate hyphae e.g. Aspergillus 

If similar conditions exists in the animal cell its referred as syncytial

Photoorganotrophs – A kind of nutritional classification of organism based on the energy and carbon source. It refers to those organisms that use light as a source of energy and organic compounds (e.g. acetate) as C source. E.g. Rhodospirillum sp., Heliobacillus.

Enrichment culture – A kind of culturing technique that allows specific bacteria that has the capacity to grow under defined conditions and become numerically dominant. E.g. enrichment of cellulose in the medium increases the numerical abundance of Cytophaga sp. (a cellulolytic bacterium).

Bacterial growth – It refers to division of one bacterium into two daughter cells through the process of binary fission, thus it is increase in the cell number.

Growth rate – It refers to the rate at which the bacteria divides, it is increase in numbers or cell mass per unit time, it is usually expressed as generation time.

Generation time – Time required for the cell population to get doubled in a given environment, assuming that the nutrient sources are not depleted.

Gravimetry or dry weight estimation – It is an analytical procedure in which the weight of analyte was estimated quantitatively. Gravimetry procedure was used for indirect estimation of the growth of fungi by weighing the biomass of fungi after their growth.

Log phase/exponential growth – It is the second stage of a growth curve. It is also called as exponential growth phase, cells grow is constant and divide at maximal rate, a balanced growth is maintained. In this stage the primary metabolites like amino acids, organic acids and alcohol.

Stationary phase/idiophase – A growth phase during which, growth ceases, the growth curve becomes horizontal, in this phase nutrient depletes, toxic products accumulate. During this phase cell synthesis secondary metabolites including low molecular weight antibiotics and high molecular weight toxins.

Balanced growth-Growth is said to be balanced when the increase in mass of all essential cell components occurs exponentially and is coincident with the rate of increase in total biomass or in cell numbers.

Diauxic or biphasic growth

When an organism was provided with two sources of carbon (glucose and lactose), it preferentially metabolizes one that is simple and more energy efficient (glucose) source (completely) before starting to metabolize the other (lactose); the two phases of growth are commonly separated by a lag phase in which the organism synthesises enzyme(s) necessary for the utilization of the second source of carbon. Such growth is termed diauxic, and the resulting growth curve is characteristically biphasic as shown in the diagram.

Gravimetry – it is an analytical chemistry based method, used in microbiology mainly for quantitative determination of fungal biomass

Nephlometry – It is kind of suspended particulates measurement in which the scattered light is measured, usually at right angles to the incidence of light. E,g, commonly used in immunology to determine the level of serum proteins.

Turbidometry – It is kind of suspended particulates measured based on intensity of the light transmitted through the medium, thus it measures unscattered light. E.g. measurement of bacterial growth turbidity.

Synchronous culture - Synchronous culture is a condition in which all bacterial cells of the population are physiologically identical and in the same stage of cell division cycle at a given time.

Fastidious organism - Any organism that has a complex nutrient requirements, they grow only if special or specific nutrients are added in the culture medium. e.g. Haemophilus influenzae - a pathogen causing meningitis and respiratory infections requires several growth factors including hemin (factor X),               NAD (factor V),thiamine, pantothenic acid (vitamins) and uracil and cysteine (nucleotides) that were provided in need to be provided in growth medium for its growth.