Question

Fill in each blank with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase can be used only once.

aerobic	ROS	Gram-negative	selective enrichment
biofilm	Gram-positive	opportunistic	anaerobic
flavonoid	Nod-factor	quorum sensing	fermentation

  
The formation of a symbiosis between bacteria and its eukaryotic host is typically highly species-specific and
therefore requires ____________________ on the part of the host. For the squid, this involves modifying its
mucous layer so that only ____________________ bacteria can bind. For legumes, this requires a membrane
receptor that binds species-specific ____________________ structures to identify its symbiont and allow
infection of roots to create a nitrogen-fixing nodule. Regardless of specific location, our human microflora is
enriched in ____________________ bacteria while the skin is also highly enriched with
____________________ species due to the abiotic stresses of this particular environment. Although our
microflora lack the virulence factors required to cause disease on their own, they can become
____________________ pathogens in a person with a compromised immune system.

Answer 1

1) The eukaryotic host has to provide selctive enrichment opportunity to the species specific symbiotic bacteria.

Selective enrichment is creating the habitat condition favourable for only a particular species of bacteria.

2) Squid hosts a quorum sensing bacteria named Vibrio fischeri by modifying its mucous layer. Quorum sensing is the process through which all bacteria in the biofilm of Vibrio fischeri communicate that helps the squid in regulating the luniminiscence of the squid according to the external conditions.

3) Species-specific Nod-factor binds with the receptor of the legume plants. The Nod-factor or nodulation factor is a chemical signal produced by particular species of bacteria that initiates the formation of the nodules in plant's roots, which the bacteria inhabits later.

4) Most of the symbioic bacteria that is hosted by the human are the grampositive bacteria.

5) The skin also hosts different species of gram negative bacteria due to abiotic stress, such as drying of skin.

6) Bacteria that are living in human can turn into opportunistic pathogens . Eg: Though most of the strains of Escherichia coli is a symbiotic but some strains can cause extraintestinal dieseases. It depends on which strain can colonize the intestinal system, and it depends on the response of our immune system also.