Tag: bacteria; benefits and harmful effects

Escherichia coli is a Gram-negative, facultatively anaerobic bacteria. It is found in the intestine of warm-blooded organisms. It has one circular chromosome. The chromosome contains double-stranded DNA. It may contain some circular plasmids as well as extrachromosomal material.

• Mitochondria are absent in bacteria and blue-green algae.
  
• A prokaryotic cell lacks membrane-bound cell organelles and nucleus whereas, a eukaryotic cell consists of membrane-bound cellular organelles and well-defined nucleus.
  
• Red algae, green algae and brown algae have eukaryotic cells (well-defined nucleus and cellular organelles).
• So, the correct answer is 'Bacteria'.

Acetabularia is a single-celled green photosynthetic algae which contain chloroplasts of the photosynthetic function. Being unicellular it has a complex shape and has been a model organism for the study of gene expression with morphogenesis. It has a large nucleus which contains a genetic material. Because of the presence of nucleus which is absent in prokaryote, these algae is classified in eukaryotes. hence algae Acetabularia is a unicellular eukaryote.

A. Amphitrichous bacteria have flagella (single or multiple) extending from both ends of the cell.

Amoeba is a unicellular organism. The main waste material in amoeba ammonia (NH$ _3$) along with carbon dioxide (CO$ _2$). The waste material is excreted through body surface (plasmalema) by the process of diffusion. In this process, contractile vacuoles play important role.

Entamoeba histolytica is a protozoan protist. It is pathogenic in nature. It resides in the upper part of the human large intestine and causes the disease known as amoebic dysentery or amoebiasis. The symptoms of the disease are abdominal pain, repeated motions with blood and mucus. Entamoeba histolytica is transmitted through food or water contaminated with cysts. A mature cyst is called quadri-nucleate cyst. It has four nuclei and two chromatid bodies. Quadrinucleate cyst is the infective stage.

Entamoeba histolytica is a protozoan protist. It is pathogenic in nature. The type of nutrition present in Entamoeba is parasitic. The parasite is generally with one pseudopodium. The contractile vacuole is absent as there is no need of osmoregulation. It feeds on red blood corpuscles by damaging the wall of the large intestine and reaching the blood capillaries. It produces ulcers. It resides in the upper part of the human large intestine and causes the disease known as amoebic dysentery or amoebiasis. Entamoeba histolytica is transmitted through food or water contaminated with cysts. A mature cyst is called quadri-nucleate cyst. It has four nuclei and two chromatid bodies. Quadrinucleate cyst is the infective stage. Only one young Amoeba with four nuclei hatches out from a cyst of Entamoeba histolytica. However, single cyst of Entamoeba histolytica produces eight Amoebae.