KINGDOM: MONERA (Prokaryotes)
- Most primitive
- Unicellular, colonial, or filamentous, prokaryotes without nuclear membrane, nucleolus, chromatin, and histone proteins
- Bacteria are the sole member of this kingdom.
- Lives in the extreme habitat where other life forms cannot survive such as hot spring, desert, snow and deep oceans.
Characteristic:
- Cell wall: Made up of peptidoglycan (amino acid +sugars) or murein (a type of mucopeptide) except in archaebacteria and mycoplasma.
- Cell membrane: i. Made up of lipoproteins (lipids + protein).
ii. Space between cell wall and membrane called as periplasmic space, the site of digestion of complex substances.
- Cytoplasm: i. Lacks membrane-bound cell organelles.
ii. The nucleus is also known as an incipient nucleus, genophore, nucleoid or fibrillary nucleus.
iii. Lacks true chromosomes, therefore the presence of false chromosome, which is made up of ds circular DNA + non- histone proteins. It forms a chromosomal region, known as nucleoid on coiling.
iv. 70s ribosomes are present.
- Mode of nutrition: There are of 2 type
A. Autotrophic nutrition B. Heterotrophic nutrition
A. Autotrophic nutrition (Use light or chemical energy): It has been further classified as
i. Photosynthetic: Use of light energy for food Synthesis, non-oxygenic and use H+, which is received from Organic and inorganic sources. Eg: Purple sulphur bacteria(Chromtium)
Green sulphur bacteria(Cholobium, thiothrix)
Purple non-sulphur bacteria(Rhodospirillum, Rhodopseudomanas)
ii. Chemosynthetic: Obtained energy for the synthesis of food by oxidising certain inorganic substances like ammonia, nitrate, nitrites, ferrous ions. Thus, they do not utilise light energy sources.
E.g. Nitrite bacteria (Nitrosomonas, nitrococcus)
Nitrate bacteria (Nitrobacter)
B. Heterotrophic nutrition(Cannot manufacture their own food): It has been further classified as
i. Saprophytic ii. Parasitic iii. Symbiotic
i. Saprophytic bacteria: obtained food from organic matter
Two types: a. Obligate saprotrophic eg. Bacillus vulgaris, clostridium botulinum
b. Facultative parasites: eg. Pseudomonas, Staphylococcus.
ii. Parasitic bacteria: Obtained food from the living organism
Two types: a. obligate parasites e.g. Mycobacterium leprae
b. Facultative saprotrophic: Mycobacterium tuberculosis
iii Symbiotic bacteria: normally parasitic but in absence of living host become saprotrophic
- E.g. Rhizobium
- Mode of respiration: it has been classified into :
A. Aerobic bacteria B. Anaerobic bacteria
A. Aerobic bacteria: Further classified into -
i. Obligate aerobic: Completely aerobic and die in absence of oxygen
Eg. Azobacter
ii. Facultative anaerobic: Aerobic bacteria but survive in absence of oxygen.
eg. Clostridium botulinum, Clostridium tetani
B. Anaerobic bacteria: Further classified into -
i. obligate anaerobic: anaerobic bacteria and do not have the capacity of aerobic respiration
Eg. Clostridium botulinum
ii. Facultative aerobic: Anaerobic but have a capacity of aerobic respiration.
E.g fermentation bacteria except for Acetobacter aceti
- Shapes:
1.Coccus/cocci: i. spherical shape
ii.Smallest bacteria
iii. Maximum resistant bacteria
Eg: Diplococcus pneumonia
2.Bacillus /Bacilli: i. Rod-shaped
Eg: E.coli, Bacillus anthracis
3.Spirillum: Spiral-shaped bacteria
Eg: Spirillum volutans, Treponema
4.Comma / vibrio : Comma-shaped bacteria
Eg: Vibrio cholera
- Reproduction: Asexual type. Bacteria reproduce mainly by asexual reproduction and also show sexual reproduction (TRUE SEXUAL REPRODUCTION IS ABSENT)
Includes two methods: A. Asexual reproduction B. Genetic recombination
A. ASEXUAL REPRODUCTION: i. Several types of asexual spores are produced by bacteria like sporangia, oidia, conidia and endospores.
ii. Most common is BINARY FISSION.
iii. Under the favourable condition, daughter cells may repeat binary fission no. of times and forms large population. But the process gradually slows down and ultimately stops due to
- Shortage of space
- Lack of nutrition available
- Accumulation of waste material
- Development of destroying bacteria
ENDOSPORE: i. Also known as “Reproduction without multiplication.
ii. It occurs during an unfavourable condition.
iii. Mostly found in bacillus type bacteria.
iv.Highly resistant to high temperature, radiations, antibiotics and chemicals due to:
- Thick and impermeable spore coat.
- Low water content.
- Low metabolic activity.
- Ca- DPA complex: The endospore consist of a central core, made up of nuclear material (DNA, RNA and proteins) and spore cytoplasm, including lipids, Ca. Mn. This core is surrounded by a membrane called cortex wall, around the wall another layer is found called cortex, mainly consist of peptidoglycan and calcium dipicolinic acid (Ca – DPA). It is an anticoagulant.
B.GENETIC RECOMBINATION: i. No gamete formation and fusion.
ii. Exchange of genetic material does not take place and is called genetic recombination.
iii. It includes three methods:
A. TRANSFORMATION B. CONJUGATION C.TRANSDUCTION
A. Transformation: i. Griffith (1929), worked on the effect of the Diplococcus or streptococcus bacteria on mice and discovered the process of transformation.
ii. Donor and recipient do not come in contact.
iii. The ability to pick up DNA from the solution is called COMPETENCE.
iv. Two strain of D. pneumonia is used i.e. capsulated or S- III (virulent strain) and non-capsulated or R-II (non – virulent strain)
Griffith concluded that something passed from the heat-killed S –III TO R –II bacteria, so that non-virulent strain changed or transformed into the virulent bacterial strain.
Avery, MacLeod and McCarty (1944) proved that DNA is the genetic material.
B. Conjugation (between F and F): i. Sort of sexual reproduction
ii. 1st discovered by Lederberg and Tatum in E.coli in 1946.
iii. Donor cell (F+) attached to the recipient cell (F-) with the help of sex pili, conjugation tube. The F factor (F - PLASMID) now replicate and the replica move toward F- through conjugation, making it F+ bacteria.
C. Transduction: i. A small amount of ds DNA is transferred from the donor to the recipient by a bacteriophage.
ii. 1st demonstrate by the Zinder and Lederberg (1952), working with Salmonella typhimurium
iii. Lytic cycle: The phage infects a bacterium, the bacterium makes lots of phages, and then kills the cell by making it lyse.
iv. The lysogenic cycle: The phage infects a bacterium and inserts its DNA into the bacterial chromosome, allowing the phage. DNA (now called a prophage) to be copied and passed on along with the cell's own DNA
Types of transduction: It is of three types:
a. Generalised b. Specialised c. Abortive transduction
a. Generalised: Here, bacteriophage can carry Genetic material from any region of bacterial DNA. E.g. T4 - phage
b. Specialised or Restricted: DNA bought by phage carry only a specific region of bacterial DNA to a recipient. E.g. Lambda phage
c. Abortive transduction: DNA bought by phage do not integrate with the genome of the recipient and is lost after one or two generation
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