Category: Biology Second Paper

protoplasts of protoplasts of protozoan bacteria divide to form smaller parts in unfavorable environment. Cytoplasm accumulates around each segment to form gonidia. New bacteria are formed from the transformed gonidia. For example, Leucothris.

Conidiophores are formed from protozoan bacteria. Conidiophores produce tiny conidia. The conidia are arranged like chains. The mature conidia detach and germinate in a favorable environment to form new bacteria. For example, Streptomyces.

1. Conidia: Conidiophores are formed from protozoan bacteria. Conidiophores produce tiny conidia. The conidia are arranged like chains. The mature conidia detach and germinate in a favorable environment to form new bacteria. For example, Streptomyces.
2. Gonidia: protoplasts of protoplasts of protozoan bacteria divide to form smaller parts in unfavorable environment. Cytoplasm accumulates around each segment to form gonidia. New bacteria are formed from the transformed gonidia. For example, Leucothris.
3. Zoospores: Bacteria produce zoospores in unfavorable environment. Zoospores produce new bacteria. Such as Azotobactor, Rhizobium.
4. Endospore: Bacterial protoplast shrinks and becomes spherical or ovoid due to lack of food in unfavorable environment. It is then enveloped by a thick coat and becomes an endospore. This is called a resting spore. New bacteria are born from resting spores under favorable conditions. For example, Bacillus subtilis, Clostridium tetanus, Escherichia coli.
5. Microcyst: Several cells of myxobacteria unite to form a swarm. Each cell of the swarm becomes a microcyst. New bacteria are born from microcysts. For example – Myxococcus fulvus, Chondromyces crocatus.

Bacteria produce one or more branches. Branches separate and live independently.

Bacteria are divided into one or more fragments for various reasons. Each fragment develops into a complete bacterium.

Bacteria form small buds. First a small bud emerges on one side. Then the nucleus gradually enlarges on one side and the nucleoid material of the original bacterium splits into two parts on the other. A fragment of nucleoid material enters the bud. The bud grows larger and splits off. For example, Ancalomicrobium adetum.

(i) At the beginning of bifurcation bacteria grow in size by consuming food. Its nucleus is also enlarged.
(ii) Bacterial DNA is located in the center of the cell and associated with the cell membrane.
(iii) Replication of DNA takes place while attached to the cell membrane.
(iv) The cell grows in length. Growth of the cell wall and cell membrane occurs between the two ends of the cell.
(v) Cell wall and cell membrane elongation causes DNA replicas to separate in two directions.
(vi) The cytoplasm of the cell folds inwards. The nucleus then divides into two fragments. The cytoplasm folds further inward. Later the cytoplasm changes into two cells with nucleus.
(vii) Due to the turgor pressure, the newly formed daughter cells separate from each other.
(viii) The daughter cells grow to equal the mother cells. Again takes part in bifurcation. This process takes 20-30 minutes.

Numerous fine hair-like appendages arise from the outer layer of gram negative bacteria. These are called pili or fimbriae. It is more numerous than flagella and shorter in length. It is made up of proteins called pilin. Conjugation tubes are formed during reproduction and are called sex pili. Gonorrhea bacteria attach to host cells by pili.

The whip-like appendages that arise from the outer layer of the cytoplasm are called flagella. The stiff flagella are called fimbriae. It is composed of flagellin protein. Its length is 4-5 nm. Flagella help bacteria to move. Each flagella has three segments. Basal body, hook and filament. Bacteria with flagella are called Tricus and those without flagella are called Atrichous.

Bacterial cells do not have a true nucleus. Its nucleus is called nucleoid or xenophore or pseudonucleus. It lacks nuclear membrane and nucleolus. The center of the cytoplasm contains a single stranded double-stranded DNA. At the center of DNA is a circular RNA. RNA is surrounded by nucleoproteins. It does not contain histone proteins. It transfers hereditary traits from generation to generation.