Microorganism Morphology

A microorganism morphology is the physical build and shape of any given microorganism, or microscopic organisms. The world is filled with billions of microorganisms and they can take on a multitude of different forms. The study of these morphologies and the microorganisms associated with them is crucial to understanding how life adapts at the most minuscule level. There are also applications in engineering; by studying organic forms, we can ourselves build useful microscopic or macroscopic infrastructures based on them or with them in the future.

Microorganism Morphology

What is a microorganism?

A microorganism is, as defined by the National Cancer Institute, "An organism that can be seen only through a microscope. Microorganisms include bacteria, protozoa, algae, and fungi. Although viruses are not considered living organisms, they are sometimes classified as microorganisms." For the purposes of this page, a virus will be considered a microorganism, due to the fact that they can have morphologies and are microscopic.

What is a morphology?

A morphology is, as defined by the National Cancer Institute, "The science of the form and structure of organisms (plants, animals, and other forms of life)." In relation to the microorganism, it is the physical build and appearance, the different possible ways it can 'morph', to which this term references.

Morphological Variations In Microbiota

There are some rather common morphologies present among the array of microbiota in the world, and there are also some very rare ones. The main bacterial cellular morphologies are the coccus (spheres), the bacillus (rod-shapes), coccobacillus (something between coccus and bacillus), and spiral. An example of coccus is Staphylococcus aureus (1). An example of bacillus is Bacillus subtilis (2). An example of coccobacillus is Coxiella burnetii (3). An example of spiral is Vibrio cholerae (4). Images of each can be found below.

Bacteria shape, in general, is incredibly diverse, and relies on the structure of the cell wall. It is not uncommon to find many different varieties even among or within the main groups, such as coccus or spiral. "While staphylococci or Neisseria cells, for example, are truly round-shaped, streptococci, lactococci or enterococci have an ovoid shape." This makes clear the sheer level of creativity with which the natural world exhibits itself on a microscopic level.

An example of rare shapes is the triangular shaped Eunotia trigona, discovered within a moist environment in Brazil.

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Evolution of Microbiota Morphologies

Bacteria that look similar to what the earliest life may have appeared to be like.

There are an abundance of microbiota and an abundance of their forms. This has occurred through the processes of evolution, where microbiota have come to be in the varieties they are today. Some research has been done on ancient microbiota. It has been considered that "Microscopically, modern tufas, sinters, and travertines (TSTs) may contain filaments, spirilla, clotted micrite (peloids and/or grumeleuse), tubules, coccoids, or spheres that suggest a biological component to their constitution." While there is little truly discrete evidence or any way of investigating the earliest of microbiota and their morphologies, some shapes have been detected in paleobiological sites. It has been concluded, though, that "only a few basic morphologies are preserved in the geological record; primarily tubules, including smooth-walled cylindrical voids (may be subsequently partially occluded), filaments, and spherule, peloidal, or coccoid-like forms." This hints at the fact that these may be the earliest and the rest descended from something like these. It could also be true that other known morphologies existed at these times and have not been found to exist at these time periods yet. It is important to point out that of the shapes found, cocci were the most unreliable, so if any morphologies are to be doubted to have existed earliest or longest, it may be the cocci, according to some experts. Overall, the general consensus is that "rod-like" morphologies were the first to appear and after that came many others, including the cocci.

Utility of Different Morphologies

Here you can see the common general differences in microscopic morphologies, at least among bacteria.

Utility in nature

There are an abundance of microbiota and an abundance of their forms. The utility of any morphology is directly related to what it needs to do, which is survive. The shapes of the microbiota are certainly evidence of their history and evolution, and their environments may be telling signs of the reason for their shapes. In other words, "...if a bacterium needs to eat, divide or survive, or if it needs to attach, move or differentiate, then it can benefit from adopting an appropriate shape." There are a few different ways in which microorganisms are "pressured" into different morphologies: nutrient acquisition, cell division, and predators. Each microorganism needs to consume nutrients. The environment they are in as well as the population size and diversity of their food will affect how, over time, they will change to better come into acquisition of these nutrients. This may involve changing size, side proportions, biological tools, or a variety of other things. The same thing applies to the problem of cell division (reproduction) and evading predators.

Utility in science and society

Morphologies have been an important thing to take into consideration in recent years. The fields of microfabrication and nanofabrication can take advantage of existing microorganisms in order to produce micro and nano structures. The variety of microbiota allow for, therefore, a variety of utilities. "These naturally grown features make microorganisms capable to act as ideal biotemplates to fabricate MNPs with controlled geometries, which can be further utilized to construct unique structures for functional materials and devices." MNP's are referencing Micro or Nano Particles. This is a growing field and much progress has already been made in the past 10 or 20 years.

Bibliography

• de Wet, C.B., Davis, K. Preservation potential of microorganism morphologies in tufas, sinters, and travertines through geologic time. Palaeobio Palaeoenv 90, 139–152 (2010). https://doi.org/10.1007/s12549-010-0027-z

Palaeobiodiversity and Palaeoenvironments is an established hybrid international journal publishing material pertaining to the title.

• Furey, Paula C., and Antonia Liess. “Substratum-Associated Microbiota.” Water Environment Research 86, no. 10 (2014): 1774–1831. https://www.jstor.org/stable/26662291.

Water Environment Research (WER) is an international journal focused on water research.

• André Zapun, Thierry Vernet, Mariana G. Pinho, The different shapes of cocci, FEMS Microbiology Reviews, Volume 32, Issue 2, March 2008, Pages 345–360, https://doi.org/10.1111/j.1574-6976.2007.00098.x

FEMS Microbiology Reviews is a microbiology-focused online journal.

• Young, Kevin D. “Bacterial morphology: why have different shapes?” Current Opinion in Microbiology 10, no. 6 (November 5, 2007): 596–600. https://doi.org/10.1016/j.mib.2007.09.009.

Current Opinion in Microbiology publishes material relating to the field of microbiology.

• Gong, D., Sun, L., Li, X., Zhang, W., Zhang, D. and Cai, J. (2023), Micro/Nanofabrication, Assembly, and Actuation Based on Microorganisms: Recent Advances and Perspectives. Small Struct. 2200356. https://doi.org/10.1002/sstr.202200356

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