Question

Richard Lenski's bacteria adapted to the laboratory environment, one lineage evolved a new trait just after 33,000–theability to feed on _______. As the bacteria evolved to eat more _______, they grew to greater numbers, which researchers identified because their flask grew cloudy. Optical density on this graph is a measure of this cloudiness.

1) citrate
2) calcium
3) glucose
4) a novel protein

Answer 1

The bacterium studied by Richard Lenski evolved to metabolize 1) citrate after 33,000 generations in a laboratory setting, revealed by an increase in optical density due to a higher concentration of bacteria in the culture flask.

Step-by-step explanation:

The experiment conducted by Richard Lenski on Escherichia coli, a type of bacterium, is a classic example of experimental evolution and adaptation. In this long-term study, one of the bacterial lineages evolved after 33,000 generations with the remarkable ability to metabolize a new food source that was not previously a significant part of its diet in the laboratory environment.

Specifically, the bacteria acquired the ability to feed on citrate under aerobic conditions, where citrate was previously only metabolized anaerobically by E. coli. As the bacterial population continued to consume more citrate, their numbers increased significantly, leading to a notable increase in the optical density of their flask, which was a measure of how cloudy the flask became due to the higher bacterial concentration.

Bacteria like E. coli are known for their various metabolic capabilities, allowing them to grow in diverse environments by utilizing different combinations of available nutrients. This plasticity in metabolic function is an important aspect of their survival and adaptation.

The success of bacteria in diverse and often extreme conditions is a testament to their complex biochemistry and the ability to utilize organic or inorganic compounds for energy. The cultivation of bacterial cultures in laboratories provides important insights into their physiology and growth characteristics, although it represents only a fraction of bacterial diversity, as many cannot be cultured under laboratory conditions.

Understanding bacterial growth and adaptability in changing environments is crucial in fields such as environmental biology, microbiology, and evolutionary biology. As lenses research demonstrates, when bacteria are introduced to new substrates or conditions, they can rapidly evolve new functions, such as citrate metabolism in an oxygen-rich environment, revealing fascinating dynamics of life and survival strategies at the microbial level.