Question

7. Find another example of microbial symbiosis in the natural world and briefly discuss this relationship. For example, what organisms are involved? How does this symbiotic association work? How is the relationship maintained between these species? Does this symbiosis benefit the environment? Are there any biotechnological applications that can be developed as a result of this symbiosis? (5pts)

Answer 1

Microbial symbiosis

Symbiosis is generally defined as a condition where two dissimilar organisms live together in an intimate associate that sees both organisms benefit. Microbial symbiosis tends to be bit broader in definition, being defined as the co-existence of two organisms.

Microbial symbiosis can be evident as several different patterns of co-existence. Relationship maintained like in the form of :-

1) One pattern is known as mutualism. In this relationship, both organisms benefit

2) Another type of relationship is called commensalism. Here the relationship is beneficial to one of the organisms and does no harm to the other.

3)Another relationship known as parasitism produces a benefit to one organism at the expense of the other organism. Parasitism is not considered to be a symbiosis between a microorganism and the host

Organisms involved:-

1) ancient bacteria and a eukaryote

2)bacteria in the intestinal tract of warm-blooded animals

3)nodules of leguminous plants and bacteria genus Rhizobium.

4) Gram-negative bacterium Xenorhabdus nematophilusand (nematode) Steinernema carpocapsae.

Symbiotic association:-

* Microbial symbiosis has been a survival feature of bacteria since their origin. The best example of this is the presence of the energy factories known as mitochondria in eukaryotic cells. Mitochondria arose because of the symbiosis between an ancient bacterium and a eukaryote. Over evolutionary time the symbiosis became permanent, and the bacterium became part of the host. However, even to the present day the differences in constitution and arrangement of the genetic material of mitochondria and the host cell's nucleus attests to the symbiotic origin of mitochondria.

*There are several well-known examples of bacterial mutualism. The first example is the presence of huge numbers of bacteria in the intestinal tract of warm-blooded animals such as humans. Fully 10 percent of the dry weight of a human consists of bacteria. The bacteria act to break down foodstuffs, and so directly participate in the digestive process. As well, some of the intestinal bacteria produce products that are crucial to the health of the host. For example. In humans, some of the gut bacteria manufacture vitamin K, vitamin B 12, biotin etc

* second example of symbiotic mutualism is the colonization of the nodules of leguminous plants by bacteria of the genus Rhizobium. The bacteria convert free nitrogen gas into a form of nitrogen called nitrate. This form of nitrogen can be readily utilized by the plant, which cannot otherwise use the gaseous form of nitrogen. The plant benefits by acquiring a readily available nitrogen source, and, as for the intestinal bacteria, Rhizobium benefits by virtue of the hospitable environment for growth.

*Mcrobial symbiosis can be exquisite. An example is the Gram-negative bacterium Xenorhabdus nematophilus. This bacterium lives in a nematode called Steinernema carpocapsae. Both organisms require the other for their survival. Thus the symbiosis is obligatory. The bacterium in fact supplies toxins that are used to kill insect that the nematode infects.

Effect to environment:-

In Ecology, biological interactions can involve individuals of the same species (intraspecific interactions) or individuals of different species (interspecific interactions). These can be further classified by either the mechanism of the interaction or the strength, duration and direction of their effects.Species may interact once in a generation (e.g. pollination) or live completely within another (e.g. endosymbiosis). Effects range from consumption of another individual (predation, herbivory, or cannibalism), to mutual benefit (mutualism). Interactions need not be direct; individuals may affect each other indirectly through intermediaries such as shared resources or common enemies.

Bio technical application result in the application of symbiosis:

1)Insect symbionts constitute a rich and mostly untapped source of bioactive small molecules as well as digestive enzymes of potential biotechnological value.

2)Even though their exploitation is currently hampered by the unculturability of most symbionts, advances in culturing techniques as well as genomic and genetic tools for the identification and heterologous expression of genes of interest may overcome this hurdle.

3) Furthermore, a large diversity of facultative associates is experimentally and/or genetically tractable and could be of more immediate applied value.

4)In addition to exploiting their metabolic capabilities, insect symbionts can be used to promote insect health as well as to target and control agricultural pest insects and vectors of medically important human diseases in an environmentally friendly way.

5)Overall, increasing research efforts in the areas of insect ecology and symbiosis not only promise to uncover interesting new symbiotic alliances but may also prove valuable in the continued effort to find new sources of biotechnologically important molecules and enzymes.

6)Specifically, targeted searches for compounds with particular applied value (e.g., antibiotics, detoxifying enzymes, cellulases, lipases, etc.) may benefit from being guided by the knowledge on host-symbiont ecology, which has the potential to predict particularly promising systems for exploration.