Intro to microbiology Flashcards
Definition of microbiology
Microbiology deals with the causative agents of infectious diseases of man, the response generated by him against them and various methods of diagnosis, treatment and prevention
Importance of Medical Microbiology
- Control of epidemics
- Vaccine production
- Production of antibiotics
- Diagnosis of infectious diseases
- Understanding of life processes: microbial biochemistry helps us to understand how individual cellular reaction were efficiently and harmoniously carried out for biological functions.
- Genetic engineering: e.g. recombinant DNA technology for insulin, human growth hormones and factor VIII production
How are organisms divided? Briefly describe
Eukaryotes are organisms
They have membrane-bound nucleus aka ‘true nucleus’ and membrane-bound organelles, microtubules and microfilaments these form a complex intracellular structures
The DNA of eukaryotes are organized into chromosomes separated by a distinct mitotic apparatus during cell division (mitotic spindle)
Prokaryotes
*They are small in size (order of 1um in diameter) and absence of nuclear membrane
*The specialized region of the cell containing DNA is called the NUCLEOID
*The DNA is a circle with a length of about 1mm which must be coiled and super coiled to fit but must be in relaxed form for DNA replication
What are Microbial eukaryotes?
Microbial eukaryotes (microscopic eukaryotes) are termed PROTISTS
Protists include four major groups namely:
-algae
-protozoa
- slime molds
- Fungi
What are Algae?
*These are photosynthetic protists producing O2 as a product of photosynthesis with the use of chloroplast
* They are not pathogenic
* They may be unicellular or multicellular appearing in filamentous forms
Protozoa
- These are unicellular, non-photosynthetic, motile protists
- They are heterotrophs; depending on organic compounds for nutritional requirement
- From flagellated protozoa appear to have evolved the amoeboid, the ciliates, those with flagella at one stage and pseudopodia at another stage and the sporozoons with complex life cycle
- Examples are Trichomonas vaginalis, plasmodium spp, Entamoeba spp, Balantidium coli
What are fungi?
Fungi are a group of non-photosynthetic, non-motile protists which exist as saprophytes, parasites or commensals
* They grow as a mass of branching interlacing filament (hyphae) known as a mycelium
* The hyphae exhibit cross-wall which are perforated, allowing free passage of nuclei and cytoplasm
* The entire organism is therefore a multinucleated mass of continuous cytoplasm (coenocyte) confined within a series of branching tubes
* They can exist as yeast or mould or both (dimorphic)
* The mycelial forms are called molds
* They reproduce by spore or conidia; asexually or sexually
* Their cell walls are made up of polysaccharides called chitin
Subdivisions of fungi
– Zygomycotina
– Ascomytina
– Basidiomycotina
– Deuteromycotina
What are slime moulds?
- Characterized by a stage in their life cycle of amoeboid, multinucleated mass of cytoplasm called a plasmodium
- The plasmodium of slime molds is similar to the mycelium of fungi as both are coenocytic.
- However, the cytoplasm of slime mold is not restricted to the branches but can flow in all directions.
- The flow of the cytoplasm is related to the direction of migration to food or chemicals
Divisions under prokaryotes
*Prokaryotes can be divided into:
- eubacteria or bacteria
- archaebacteria. Archaebacteria exist in unusual conditions and are not pathogenic, they possess non-coding regions (introns) within the genes
What are bacteria?
Free living, microscopic, unicellular organism capable of performing all the essential functions of life such as growth, metabolism, etc
*They are prokaryotes, lacking membrane bound nucleus
*They posses both DNA and RNA and lack chlorophyll
* Ribosomes are 70s in size, consisting of 50s and 30s subunits
* They do not possess mitochondria, endoplasmic reticulum, Golgi body/ apparatus, no histones present
* Their double stranded DNA appear in haploid form
* Most have circular DNA
Are bacteria photosynthetic?
Generally no, however, some, e.g. the blue-green bacteria and the cyanobacteria can photosynthesize with the use of chromatophore
Other infectious agents of medical importance are:
- Viruses
- Prions
- Viroids
What are viruses?
- In a sense, viruses can be regarded as a genetic extension of its host
- Small known infectious agents of the order of 10-300nm
- Consists of capsid (protein shell) enclosing nucleic acid genome which is either DNA or RNA
- They may or may not contain external lipid layer called envelop
- The capsid protects the nucleic acid and facilitate attachment and penetration of the host cell by the virus. They are inactive outside their susceptible host
*Inside the cell, viral nucleic acid redirects the host’s enzymes to replication of the virus
*In the maturation process, newly synthesized nucleic acid and protein subunits develop into mature viral particles before beig released into the extracellular environment
What are Prions?
- These are infectious proteinaceous material
- These include:
–Scrapie: infectious degenerative central nervous disease of sheep
–Bovine spongiform encephalopathy (BSE) In cow
–Creutzfeldt-Jakob disease (CJD) has been associated with human exposure to BSE in the UK and France
