Question

Microbiologists have announced the discovery of over 30 new species of bacteria that thrive between the teeth and gums of humans. The bacteria could not be grown in the researchers' laboratories, nor were any of them ever observed via any kind of microscopy. If they couldn't culture them or see them, how could the researchers know they had discovered new species? If they couldn't examine the cells for the presence of a nucleus, how did they determine that the organisms were prokaryotes and not eukaryotes?

Short answer

Researchers can identify new species and determine if they are prokaryotes or eukaryotes by using DNA sequencing. This method involves extracting and analyzing the DNA of the microorganisms. Each species has a unique DNA sequence, allowing researchers to identify new species by comparing the 'DNA fingerprint' with those of known species. Prokaryotes and eukaryotes can be differentiated by the structure and sequence of their DNA.

Step-by-step solution

Understand Microbial Identification Methods

Researchers utilize molecular techniques, specifically DNA sequencing, to identify new species. They extract and sequence microbial DNA from samples taken from between human teeth and gums. This DNA can provide them with a unique genetic signature that is associated with specific species.

Identify Species Using DNA Sequencing

Each species has a unique genetic signature in their DNA – this is sometimes referred to as a 'DNA fingerprint'. By comparing this 'fingerprint' with those of known species, researchers can identify if the genetic material belongs to a known species or a new one. In this case, if the 'fingerprint' does not match any known species, it is likely they have discovered a new species.

Determine Prokaryote vs Eukaryote

The determination of the organisms as prokaryotes vs eukaryotes can also be inferred from the DNA sequences. Eukaryotic and prokaryotic organisms have different DNA structures and sequences. Prokaryotic DNA is typically circular and not bound within a nucleus, whereas eukaryotic DNA is linear and contained within a nucleus. These differences can be detected through DNA sequencing.

Key concepts

DNA Sequencing

DNA sequencing is a fascinating and powerful tool in the field of microbiology. It involves decoding the order of nucleotides in DNA, which are the building blocks of genes that make up the genetic blueprint of life. This process allows researchers to identify microorganisms without needing to see or culture them in a lab. To sequence DNA, scientists first extract the DNA from samples, in this case from between human teeth and gums. They then use advanced technologies that "read" the sequence of nucleotides. Often, this data is analyzed through bioinformatics tools to find patterns or "DNA fingerprints," which are unique to each species.
This fingerprint acts like a barcode that identifies which species the DNA belongs to. If it doesn't match any known species, scientists may have discovered a new one. This method is not only precise but also faster and more economical than traditional morphology-based identification methods. Thus, DNA sequencing is crucial in discovering and identifying new bacterial species, particularly those that cannot be grown in lab cultures.

Prokaryotes

Prokaryotes are a diverse group of microorganisms that include bacteria and archaea. They are known for their simple cellular structure, lacking a nucleus and other membrane-bound organelles that are characteristic of eukaryotic cells. Prokaryotic DNA is distinctive in its circular shape, as opposed to the linear DNA seen in eukaryotes. This circular DNA often floats freely within the cell, since there is no nucleus to contain it.
Prokaryotes reproduce through simple processes like binary fission, which allows them to multiply rapidly in favorable conditions. Understanding these organisms is critical because they are involved in numerous biological processes, from nitrogen fixation in the soil to the human microbiome's complex dynamics. They play a vital role in ecosystems and human health. DNA sequencing helps clarify their classification, offering insights into their evolutionary relationships and adaptations.

Eukaryotes

Eukaryotes are organisms whose cells have a nucleus enclosed within membranes. Unlike prokaryotes, eukaryotic cells contain multiple complex structures or organelles, such as mitochondria and the Golgi apparatus, which perform various specialized functions. Eukaryotic DNA is linear and resides within the nucleus, providing the cell with more control over gene expression. This structured organization allows for intricate regulatory processes, supporting the development of multicellular organisms and complex tissues.
Eukaryotes include familiar organisms like plants, animals, and fungi, and play a crucial role in the Earth's ecosystems. When identifying if a microorganism is eukaryotic, scientists look for DNA sequences characteristic of such structural complexity. DNA sequencing helps pinpoint these elements and differentiate them from prokaryotic counterparts. This identification is vital in understanding ecological roles and evolutionary relationships among living organisms.