The large-scale break-outs or blooms of blue-green algae, which is also known as cyanobacteria, presents huge environmental problems. This widespread algal growth across water bodies is known as an algal bloom. Algal blooms are a completely unfavorable event as they cause depletion of oxygen supply and reduction of light penetration, which in turn, negatively affects aquatic flora and fauna. Recently, scientists have developed a new mass spectrometry method that can identify early signs of cyanobacteria in water bodies.
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Importance of Early Detection of Blue-Green Algae in Waterbodies
Algal bloom across water bodies results in a reduction in oxygen supply and light penetration that are essential for the survival of aquatic organisms. Additionally, several algae produce toxins, e.g., hepatotoxins, that are extremely harmful to both humans and animals. Cyanobacteria can thrive in varied adverse conditions, such as extreme heat, pH, and saline environments, and this indicates that algal bloom is a global problem.
One of the prime reasons why early detection of cyanobacteria is important is because these algae grow rapidly and, thereby, early detection would help prevent its spread all over the water body. Early detection could also restrict contamination of water sources with toxins. However, this is not an easy task, as thousands of species of algae could be present and not all are harmful. Some algal species are a vital part of many water systems.
Different Methods for the Detection of Blue-Green Algae
Conventionally, light microscopy has been used to detect cyanobacteria. It was also used to classify cyanobacteria species in accordance with their morphology. One of the limitations of using the microscopic technique is that it is difficult to differentiate one species of cyanobacteria from the other, as similar morphologies co-exist.
16S rRNA genes have also been used for taxonomic identification. This technique is useful when a pure culture of cyanobacteria is obtained. However, in many instances, cyanobacteria are in a symbiotic relationship with other microbes, which makes obtaining a pure culture of cyanobacteria a challenging and time-consuming task. Although metagenomics has successfully overcome the aforementioned challenge, analyzing metagenomic data requires high-level expertise that is not always readily available.
In clinical settings, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been used to detect bacteria, fungi, and protozoa. Although this tool is rapid and easy to operate, it has been seldom used to detect cyanobacteria. In a few instances, this technique has been used to differentiate cyanobacterial strains based on ribosomal proteins. However, only skilled personnel can analyze the spectral features of these proteins.
As the accuracy and speed associated with mass spectroscopy are unquestionable, researchers believe the development of simplistic mass spectrometric methods could be extremely useful for the early detection of cyanobacteria.
Mass Spectroscopy and Detection of Blue-green Algae
Scientists at the University of Birmingham, in collaboration with researchers at the Culture Collection of Algae & Protozoa (CCAP), based at the Scottish Association of Marine Science, have developed a new mass spectrometry method that enables the detection of early signs of blue-green algae in water bodies. They have designed a new approach where key proteins or biomarkers that are unique to particular algal species could be detected using mass spectroscopy. This approach enables rapid detection of algal species.
Here, researchers developed a simple native mass spectrometry approach that comprises the advantages of MALDI-TOF MS technology in terms of its speed and ease of use. Native mass spectrometry depends on the preservation of proteins and protein complexes into the gas phase, facilitating the detection of proteins in their biologically functional state. Recently developed high-resolution instruments have been incorporated, which can detect a small amino acid substitution in one protein subunit out of the entire protein complex. This principle also helps differentiate between cyanobacterial strains.
Scientists used phycobilisomes, an abundantly present photosynthetic component in cyanobacteria, in their design of mass spectroscopy. As all the phycobiliprotein subunit amino acid sequences associated with the cyanobacteria genome are different, it could act as a marker to identify different blue-green algae.
The mass spectroscopic high-resolution technique enabled researchers to produce highly specific fingerprints that correspond to a specific type of blue-green algae. It is also able to detect a mixture of different cyanobacteria at a low pre-bloom level. Therefore, scientists are optimistic that this technique could help prevent algal bloom and protect the aquatic organisms from it.
According to Dr. Aneika Leney, lead author of this study, this analytical method would help differentiate toxic species from non-toxic species of algae, and thereby, it could keep harmful algae away from waterbodies without affecting the harmless ones.
Future Research and Development
One of the challenges faced by the researchers is the lack of available cyanobacteria genome sequences. Therefore, in the future, researchers are set to create a large database of spectral fingerprints for all the different cyanobacteria species currently known. This could enable cyanobacterial field samples to be compared with this library and generation of a metric based on the match between the spectra.
A spectrum match with 0.01% mass accuracy would confirm the presence of a specific species in a water sample containing blue-green algae. This technique has the potential to expedite the detection process of algal species during pre-algal bloom. Automation of data analysis would also facilitate non-specialists to detect cyanobacteria in water samples. Scientists claimed that this technique could also be used to determine the purity of cyanobacterial products, for example, spirulina extracts are popularly utilized as food and health supplements.
References and Future Reading
Michael, I. (2021) Native mass spectrometry identifies harmful blue-green algae. [Online] Available at: https://www.spectroscopyeurope.com/news/native-mass-spectrometry-identifies-harmful-blue-green-algae
Sound, K.J. et al. (2021) Rapid Cyanobacteria Species Identification with High Sensitivity Using Native Mass Spectrometry. Analytical Chemistry. 93(42). pp.14293–14299, https://doi.org/10.1021/acs.analchem.1c03412
Massey, Y.I. et al. (2020) A Mini-Review on Detection Methods of Microcystins. Toxins. 12, 641; https://doi.org/10.3390/toxins12100641
S, Li-Wei. et al. (2017) Rapid Classification and Identification of Microcystis aeruginosa Strains Using MALDI–TOF MS and Polygenetic Analysis. Plos One. 12(1): e0170637. https://doi.org/10.1371/journal.pone.0170637
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