Viruses are acellular organisms that consist of a nucleic acid core (either DNA or RNA) surrounded by a protein coat called a capsid
. Some viruses also possess an outer lipid envelope derived from the host cell membrane.Members of Chlorophyceae (green algae) are characterized by the presence of chlorophyll a and b, stored food in the form of starch, and cell walls primarily composed of cellulose
.Criteria for Grouping Microorganisms:
Microorganisms are grouped based on several taxonomic criteria including morphology (shape, size, flagella), staining characteristics (Gram reaction), physiological/biochemical properties (oxygen requirement, enzyme production), and molecular characteristics (16S rRNA sequencing)
.Features of Fungal Groups:
Bacterial Morphology:
Bacteria exhibit diverse shapes: Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral), and Vibrio (comma-shaped)
. They may exist as single cells, pairs (diplo-), chains (strepto-), or clusters (staphylo-).Bacterial Cell Structure:
Microorganisms are categorized based on their energy and carbon sources: Photoautotrophs (light/CO2), Photoheterotrophs (light/organic carbon), Chemoautotrophs (inorganic chemicals/CO2), and Chemoheterotrophs (organic chemicals/organic carbon)
.Transduction is a process of horizontal gene transfer in bacteria where DNA is transferred from a donor cell to a recipient cell by a bacteriophage (virus)
.(i) Growth curve in microbes:
When bacteria are grown in a closed system, they follow a predictable pattern consisting of the Lag phase (adaptation), Log/Exponential phase (rapid division), Stationary phase (growth = death), and Death phase (nutrient depletion)
.(ii) Generation time:
The time required for a bacterial population to double in number during the log phase is called generation time (or doubling time)
. It varies significantly depending on the species and environmental conditions.Bacterial Conjugation:
Conjugation is the direct transfer of DNA between two bacterial cells that are in physical contact, typically mediated by a sex pilus and a fertility (F) plasmid
.Bacterial Transformation:
Transformation is the process by which a competent bacterial cell takes up "naked" DNA fragments from its surrounding environment and incorporates them into its own genome
.Sterilization is the absolute destruction or removal of all forms of microbial life, including highly resilient bacterial endospores and viruses, from an object or environment
.Inoculation is the intentional introduction of microorganisms into a sterile culture medium to initiate growth and cultivation
.An autoclave uses pressurized steam (typically 121°C at 15 psi for 15-20 minutes) to achieve sterilization. It is the most effective and reliable method for heat-stable biological materials.
Chemical sterilization involves using gaseous or liquid agents to kill microbes. Common methods include:
(i) Culture Media:
Media provide the necessary nutrients for microbial growth. Types include Synthetic (defined), Complex (undefined), Selective (supports specific microbes), and Differential (distinguishes between microbes).
(ii) Preparation of Pure Culture:
The goal is to isolate a single species from a mixed population. Common techniques include the Streak Plate method (dilution across agar surface), Pour Plate method, and Spread Plate method to obtain isolated colonies.
MALT (Mucosa-Associated Lymphoid Tissue) is a system of lymphoid tissue found in various submucosal membrane sites of the body, such as the gastrointestinal and respiratory tracts, providing local immune protection
.(i) B-cell activation:
Occurs when a B-cell receptor (BCR) binds to its specific antigen. This often requires additional signals from Helper T-cells (T-dependent activation), leading to clonal expansion and differentiation into plasma cells and memory cells.
(ii) Heavy chain gene transcription:
Involves the V(D)J recombination process where specific gene segments (Variable, Diversity, Joining) are rearranged to form a functional heavy chain gene, which is then transcribed into mRNA for antibody synthesis
.Immunoglobulin (Antibody) Structure:
Antibodies are Y-shaped proteins consisting of four polypeptide chains: two identical heavy chains and two identical light chains, held together by disulfide bonds
. Each chain has a constant region and a variable region that forms the antigen-binding site.T-cell receptors (TCR):
The TCR is a membrane-bound protein on T-lymphocytes that recognizes processed antigen fragments presented by MHC molecules. It typically consists of an alpha and a beta chain.
Autoimmune diseases result from a failure of the immune system to distinguish between "self" and "non-self," leading to the immune system attacking the body's own tissues and organs
.MHC (Major Histocompatibility Complex) molecules are cell surface proteins that display antigen fragments to T-cells. MHC Class I is found on all nucleated cells, while MHC Class II is found on specialized antigen-presenting cells.
SLE is a chronic systemic autoimmune disease where the body produces antibodies against its own DNA and nuclear proteins, leading to widespread inflammation and damage in joints, skin, and kidneys
.HIV Life Cycle:
Hashimoto's Syndrome:
An autoimmune disorder where the immune system attacks the thyroid gland, causing chronic inflammation (thyroiditis) and often leading to an underactive thyroid (hypothyroidism)
.(i) ELISA (Enzyme-Linked Immunosorbent Assay):
A biochemical technique used to detect the presence of an antigen or antibody in a sample using an enzyme-linked detection system, producing a color change proportional to the concentration
.(ii) RIA (Radioimmunoassay):
A highly sensitive in vitro assay technique that uses radioisotopes (instead of enzymes) to measure the concentration of antigens or antibodies in biological fluids
.