Which of the following is a non-symbiotic biofertilizer?

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Non-symbiotic nitrogen-fixing bacteria are nitrogen-fixing bacteria that are free-living soil bacteria and are not directly associated with plants. These bacteria fix nitrogen from the atmosphere and provide it to the crop plants. Examples of free-living non-symbiotic nitrogen-fixing bacteria are Azotobacter, Azospirillum, etc.

What is the size of the plasmid pBR322?

[HDquiz quiz = “1956”]

pBR322 is a circular double-stranded plasmid widely used as a cloning vector for E. coli. The plasmid pBR322 was created at the University of California, San Franciso, the USA in 1977. The plasmid pBR322 is 4361 bp or 4.36 kb in length. The plasmid has two antibiotic resistance genes (ampicillin, tetracycline) and an origin of replication.

Which of the following is not true for prokaryotes?

[HDquiz quiz = "1951"]

Prokaryotes (Bacteria) possess peptidoglycan in their cell wall. They also reproduce asexually through binary fission. The protein synthesis in prokaryotes is performed through 70S ribosomes that form by the assembly of 30S and 50S ribosomal subunits. However, prokaryotes do not possess single-stranded DNA and a nucleus. Single-stranded DNA is present in a few viruses such as Parvoviruses, Canine parvovirus, Alphatorquevirus etc.

 Diphtheria toxin was discovered by

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Diphtheria is caused due to the Gram +ve bacterium Corynebacterium diphtheria. The bacterium first discovered by  German scientists Edwin Klebs and Friedrich Löffler in 1884.

The exotoxin released by Corynebacterium diphtheria is known as Diphtheria toxin. The toxin is discovered by Pierre Paul Émile Roux and Alexandre Emile Jean Yersin in 1888.

The diphtheria antitoxin was discovered by German biologist Emil von Behring for which he was awarded the first  Nobel Prize in Physiology or Medicine in 1901.

Which one is correctly matched?

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The correctly matched pair is AIDS virus-Reverse transcriptase.

Acquired Immune Deficiency Syndrome is caused due to the Human Immunodeficiency Virus (HIV) in humans. HIV is a retrovirus belonging to the family Retroviridae. The genome of HIV consists of two single-stranded positive-sense RNA enclosed inside a capsid.

To replicate its RNA, HIV uses an enzyme called Reverse transcriptase. The enzyme Reverse transcriptase generates complementary DNA (cDNA) using the viral RNA as a template. The process of synthesis of DNA from RNA is called Reverse Transcription.

Which of the following is not characteristic of Gram-positive bacteria?

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According to Gram-staining, bacteria are divided into Gram-positive or Grma-negavtive bacteria. Gram-staing mostly differentiate the architecture of cell wall and gives a positive or negative result. The characteristic features of Gram-positive bacteria are

  1. The cell wall is made up of single-layered (capsule)and smooth in nature.
  2. Gram-positive bacteria possess flagella and the basal body rings supports it.
  3. Mesosome (infolding of plasma membrane) is prominantly observed in the Gram-positive bacteria.

However, the Gram-positive bacteria lacks the outer membrane. Gram-negative bacteria contain an outer mebrane that contain lipopoly saccharides.

Prokaryotic genetic system has

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In the prokaryotes such as bacteria, the genetic system or the genetic material consists of a single circular chromosome made up of DNA. Due to the absence of a nucleus in prokaryotes, the genetic material is not present inside the nucleus.

Unlike eukaryotic DNA that binds with basic proteins histones (H2A, H2B, H3, H4, and H1) to form a structure known as nucleosome, the prokaryotic DNA lacks histone proteins (except the domain Archaea).

The main function of histone is to package the eukaryotic DNA in a smaller space. In the prokaryotes, they package their DNA in a small space by supercoiling.

Ergotamine tartrate extracted from Claviceps is used for the cure of

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Claviceps purpurea is a pathogenic fungus belonging to the family Clavicipitaceae. The fungus grows on the rye and other cereal crops. Ergotamine is a secondary metabolite/ergot alkaloid the ergot fungus Claviceps purpurea. Ergotamine tartrate (C70H76N10O16, molecular weight: 1313.4) is the tartrate salt form of the alkaloid ergotamine.

The alkaloid ergotamine tartrate is used as a medicine to treats migraine headaches. The alkaloid is used earlier for the treatment of headaches but now the drug is not available.

Which antibiotic inhibits the interaction between tRNA and mRNA during bacterial protein synthesis?

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Tetracyclines are bacteriostatic antibiotics and are very effective against multiplying microorganisms. Tetracycline passively crosses the bacterial membrane through porin channels and inhibits protein synthesis.  Tetracycline binds to the 30S ribosomal subunit of bacteria and inhibits the binding of aminoacyl tRNA to the A site of the ribosome. Thus, the antibiotic prevents the binding of tRNA to the mRNA and inhibits protein synthesis.

Tetracyclines are a group of broad-spectrum antibiotics isolated from my Streptomyces bacteria (Streptomyces aureofaciens) and effective against Gram-positive and Gram-negative bacteria. Chlortetracycline is the first tetracycline antibiotic to be discovered by Indian biochemists Yellapragada Subbarow and American plant physiologist Benjamin Minge Duggar in 1945 at Lederle Laboratories.

Which of the microorganisms is used for production of citric acid in industries?

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The microorganism used for the production of citric acid (HOC(CO2H)(CH2CO2H)2) at the industrial level is Aspergillus niger. Aspergillus niger is a fungus belonging to the division Ascomycota. The fungus causes a fungal disease called “black mold” on many fruits and vegetable plants.

Citric acid (E330) is used widely as a flavoring agent and preservative. James Currie, an American food chemist in 1917 discovered that the fungus Aspergillus niger can be used for the production of citric acid. At the industrial level, the Aspergillus niger grows in glucose or sucrose-containing medium to produce citric acid. Aspergillus niger is also used for the industrial production of  gluconic acid (E574).