Structure and Function

TWiM #276: Bacterial multicellularity near an underground stream

Podcast and Annotation Information
  • Annotation by Melissa Flores, Julia Moritz, Parth Sharma, and Ines Rauschenbach
  • Podcast audio by TWiM: Listen to TWiM #276 Podcast
  • Podcast transcript by Otter.ai and edited by  Nick Bellavia and Laurel Thompson: Access Podcast Transcripts
  • Papers Discussed:
    • Mora C, McKenzie T, Gaw IM, Dean JM, von Hammerstein H, Knudson TA, Setter RO, Smith CZ, Webster KM, Patz JA, Franklin EC. 2022. Over half of known human pathogenic diseases can be aggravated by climate change. Nature Climate Change. 12(9):869–875. https://rdcu.be/ePoTW
    • Mizuno K, Maree M, Nagamura T, Koga A, Hirayama S, Furukawa S, Tanaka K, Morikawa K. 2022. Novel multicellular prokaryote discovered next to an underground stream. Elife. 11:e71920. https://doi.org/10.7554/eLife.71920

1. Paper Abstracts

1.1. Snippet paper; discussion starts at 04:03 minutes

The Most Interesting Things (according to students)

  • Although the paper focused on aggravated pathogens, it was interesting that the podcast authors also mentioned nine pathogens significantly diminished by climatic hazards such as floods. An example they discussed was Schistosomiasis, a disease that affects both humans and animals caused by parasitic worms. Snails are the vectors for this disease, and when floods occur, the snails are killed off, therefore lowering the incidence rate of this disease.
  • We also found it interesting that some disease cases are reported to be low but actual occurrences may be higher due to misdiagnosis. They discussed Anisakiasis, a gastrointestinal zoonotic parasitic disease caused by the consumption of nematodes through raw or undercooked seafood. Cases are usually passed off as gastrointestinal upset due to the low severity of symptoms in humans and larvae are unable to survive for long periods in the humans.
  • We thought, overall the interactive sand key plot available as an interactive data collection and analysis was a really interesting and unique thing. Students would find this really interesting!

Abstract

The abstract cannot be copied due to licensing restrictions. Please see licensing information and links to the article at the journal’s web page and/or PubMed in Section 8.1.

1.2. Main paper; discussion starts at 34:36 minutes

The Most Interesting Things (according to students)

  • A podcast member asked, “How do you define multicellular?” It was interesting to hear the different definitions and opinions each person had in regard to this, and it should be noted there is no clear-cut definition to bacterial multicellularity. Bacteria can interact in numerous ways, whether it be ingesting other bacteria, multiple cells living together with different functions, biofilms, or mat formation and it is up to the scientist to explain how bacteria can be multicellular. They stated “no microbe is an island, ” which we thought was a great metaphor for this topic.
  • We found the discussion regarding the dimorphism life cycle of HS-3 to be fascinating. The liquid-crystal-like cell organization during the filamentous growth stage, and the release of lactobacilli when submerged in water, reflected an amazing adaptation to the oligotrophic conditions of the cavern with its recurring floods. This really emphasized how environmental pressures influence microbial morphology and functional evolution.
  • We found the scientific process of discovering the qualitative traits of HS-3’s life cycle very interesting. The specific culture media and GFP-tagging revealed a lot of information about this organism, and it is nice to see these techniques being utilized in the scientific world.

Abstract

“A diversity of prokaryotes currently exhibit multicellularity with different generation mechanisms in various contexts of ecology on Earth. In the present study, we report a new type of multicellular bacterium, HS-3, isolated from an underground stream. HS-3 self-organizes its filamentous cells into a layer-structured colony with the properties of a nematic liquid crystal. After maturation, the colony forms a semi-closed sphere accommodating clusters of coccobacillus daughter cells and selectively releases them upon contact with water. This is the first report that shows that the liquid-crystal status of cells can support the prokaryotic multicellular behavior. Importantly, the observed behavior of HS-3 suggests that the recurrent intermittent exposure of colonies to water flow in the cave might have been the ecological context that cultivated the evolutionary transition from unicellular to multicellular life. This is the new extant model that underpins theories regarding the role of ecological context in the emergence of multicellularity.” (Mizuno et al. 2022).

2. Vision and Change Core Concepts and 2024 ASM Fundamental Statements

 Snippet Main

Vision and Change Topics
  • Microbial Ecology (V&C_ME)
  • Impact of Microorganisms (V&C_IM)
  • Evolution (V&C_E)
  • Structure and Function (V&C_SF)

ASM Fundamental Statements
  • Fundamental Statement 23 (ASM_23):The health of the environment and all organisms (microbes, plants, humans, other animals) are closely linked and interdependent, as described by the One Health paradigm.
  • Fundamental Statement 28 (ASM_28): A minority of microbes are pathogens that can cause diseases and harm host organisms, society, and ecosystems.
  • Fundamental Statement 3 (ASM_3): The evolution of microbes is impacted by their interactions with the environment and a variety of ecological forces, including other microbes, humans, and habitats.
  • Fundamental Statement 7 (ASM_7): Microbes have evolved structures adapted for specific functions that are often associated with a fitness advantage in a particular environment.

3.  Potential Learning Objectives for the Podcast

The student will be able to:

Paper1

Order2
  • Recall how climatic hazards impact pathogenic disease in humans.

S

L
  • Predict how a certain environmental condition will influence the spread of disease.

S

H
  • Define multicellularity.
  • Identify the benefits of biofilm formation to a bacterial community.

M

L
  • Hypothesize how oligotrophic conditions lead to evolutionary adaptation.

M

H

1 Papers: Snippet (S) or Main (M)

2Learning Objectives: Lower Order or Higher Order (H)

4. Techniques Described (with Time Stamps)

4.1. Snippet Paper

  • Data Visualization (9:00–11:40): This is a way to represent data and can include bar graphs, box plots, heatmaps, etc.  Here, the authors use a visualization called a Sankey plot to display relationships and proportions of various pathogenic diseases aggravated by specific types of climate hazards.

4.2. Main Paper

  • Fluorescent Microscopy and Fluorescent Tagging (47:36–51:35): This is a type of microscopy that is used to visualize molecules or cells that have been tagged with a fluorescent group in a number of possible ways.  Here, the HS-3 strain was electroporated and tagged with green fluorescent protein to visualize the HS-3 colonies and their dispersion when flooded.
  • Bioprospecting (45:30–47:00): This is the process of exploring and studying microorganisms for potential applications in medicine, agriculture, or biotech. This approach depicts the diversity of microbes in natural environments that are poorly understood. This research group went bioprospecting in oligotrophic caves, where strain HS-3 was found on a “dripping” limestone cave wall in the Hirao karst plateau in Japan.
  • Culturing (47:40–49:00): This is the method to grow a species in a laboratory setting.  Because different species have different metabolic and physical requirements, it can be very specific for the species. The HS-3 strain was cultured in specific media called R2A because it matched some of the aspects of the environment the bacteria was found in. This media is used for primarily waterborne microbes. The colonies appeared transparent and iridescent.

5. Connections to General Microbiology Processes/Concepts (with Time Stamps)

5.1. Snippet Paper

  • Epidemiology and Public Health (5:46–8:40): Climate hazards profoundly impact infectious diseases, altering the geographic distribution, seasonality, and intensity. Rising temperatures, lack of rain, and natural disasters have created conditions for an increase in disease vectors such as mosquitoes and ticks, leading to the larger spread of diseases like malaria, dengue, and Lyme disease. Additionally, habitat disruptions by these natural disasters force wildlife closer to human populations, increasing the risk of zoonotic disease spread. Early warning systems can surveillance climate data, vector populations, and disease outbreaks to try and control these increasing disease spread risks. These warning systems can even serve as a form of pandemic prevention to aid global health in the midst of climate-induced disease severity.
  • Surveillance, Prevalence, Incidence (10:57–19:50): An interactive Sankey plot provides a valuable database for over 3,000 cases of pathogenic diseases implicated to be affected by climatic hazards. The authors link.

5.2. Main Paper

  • Biofilm vs Planktonic Growth (46:15–51:30): Although not a traditional biofilm/ planktonic interaction, the talkers discuss the current definition of multicellularity, and how it may apply to this microorganism, HS-3. HS-3 can survive in an oligotrophic cave environment thanks to its unique multicellular structure, which can then disperse as coccobacilli after being flooded.
  • Regulation of Gene Expression (52:50–53:06): Bacteria often lose adaptations when cultivated in the lab because the controlled environment lacks the selective pressures in their natural habitats. Bacteria can face challenges such as nutrient scarcity, competition with other microbes, and environmental stressors like fluctuating temperatures or water levels, in this case in the caverns. These pressures drive the evolution and gene expressions of specialized adaptations such as the dimorphism described in the paper. In contrast, lab conditions typically provide abundant nutrients, stable temperatures, and an absence of competitors, reducing the need for certain genes or traits. Over time, the bacteria may evolve to optimize growth under lab conditions which is why it is important to study bacteria in conditions that closely mimic their natural environments to understand the gene expressions that lead to these adaptations fully.

6. Podcast Questions

  1. What percentage of human pathogenic diseases are aggravated by climate change, as outlined by the 10 common climate hazards?
    1. 30%
    2. 58%
    3. 66%
    4. 72%
  2. How could human displacement due to storms, floods, wildfires, etc. influence the spread of disease?
    1. People may lose their homes, family, jobs, and belongings.
    2. There would be limited resources available to people.
    3. People would experience physical, mental, and emotional trauma.
    4. Migration to relief shelters would increase human proximity in vulnerable states.
    5. Sea level rise decreases salinity, which promotes the growth of pathogens.
  3. Which of the following are ways a bacterial community benefits by forming biofilms? [pick all that apply]
    1. Protection from environmental conditions
    2. Structural protection by adhesion to surfaces
    3. Reduced water retention ability of biofilm
    4. Community interactions within the biofilm
    5. Shared cytoplasm and ATP production
  4. How is “multicellularity” commonly defined?
    1. Asexual reproduction
    2. Aggregates
    3. Having multiple cells
    4. Having multiple, differentiated cells
  5. Oligotrophic environments are those that have low nutrient availability.  What statement below describes how these environments promote evolutionary adaptation?
    1. Organisms with motility move in and out of the poor environment.
    2. Organisms that survive there will evolve better ways to survive.
    3. Organisms directly compete with others for rich resources.
    4. Organisms will have enhanced mutations and evolve new features.

7. Figure Reading Exercises

The following are two figure reading exercises, one from the snippet paper (Figure 3) and one from the main paper (Figure 4DE).

7.1. First Figure Reading Exercise

7.1.1. Learning Objectives

Students will be able to:

  • Identify key features of a Sankey diagrams as related to these data.
  • Analyze the data to make conclusions about how climate hazards impact route of transmission and pathogenic diseases.
  • Predict how a certain environmental condition will influence the spread of disease.
Experimental Background (Mora et al., Figure 3)

The impact of climate change on human health, specifically how various climatic hazards can aggravate pathogenic diseases, is significant because understanding the links between climate change and disease spread can help develop better public health practices. Here, Mora et al. (2022) investigated how different climate events affect pathogenic bacterial diseases. Their data are collected from more than 77,000 scientific reports of disease and climate events where they could be directly linked in time or location. Their results are displayed as a Sankey diagram that visualizes the contributions of climate hazards (left) to specific modes of infection (middle) and specific pathogens (right).  For help with interpreting Sankey diagrams, see: https://seeingdata.org/taketime/inside-the-chart-sankey-diagram/

  • This article is not licensed for Creative Commons use; see copyright information. Thus, figure 3’s image and abstract cannot be copied here.

7.1.2. Questions

  1. What does the color of the vertical bar indicate?
    1. The severity of disease symptoms
    2. The frequency of reported outbreaks
    3. The proportional quantity of diseases
    4. Economic cost of disease outbreaks
  2. What does the thin/thickness of the line connecting different sections of the diagram indicate?
    1. The relative proportion of each section represented in the other sections
    2. The severity of disease symptoms for each of the pathogenic diseases
    3. The frequency of reported disease outbreaks for each year and region
    4. Economic cost of disease outbreaks since the beginning of this data collection
  3. What eukaryotic group had the least number of diseases associated with it?
    1. Animals
    2. Chromists
    3. Fungi
    4. Plants
  4. How many diseases found in this study were caused by prokaryotes?
    1. 78
    2. 91
    3. 23
    4. 69
  5. Which transmission pathway shows the highest number of pathogenic diseases affected by climate hazards?
    1. Vector-borne
    2. Water-borne
    3. Food-borne
    4. Airborne
  6. If there was an increase in precipitation that caused flooding, which transmission path and pathogen group would likely increase based on these data?
    1. Vector-borne; Viruses
    2. Waterborne; Bacteria
    3. Vector-borne; Bacteria
    4. Waterborne; Fungi
    5. Food-borne; Protozoans

7.2. Second Figure Reading Exercise

7.2.1. Learning Objectives

Students will be able to:

  • Identify key features in the microscopy images and model life cycle drawings.
  • Analyze the coordinating images and life cycle to map the images to life stage.
  • Analyze the life cycle drawings to define life cycle features.
  • Design an experiment to determine if cells released in lab conditions are similar to cells released in natural conditions.
Experimental Background (Mizuno et al., Figure 4DE)

Multicellularity in bacteria is not common, but Mizuno et al. (2022) have isolated and identified a bacterium with this capability, Jeongeupia sacculi sp. nov. HS-3, which was collected from a cave wall known to flood intermittently. To characterize its lifecycle and growth, the researchers simulated these growth conditions in the lab and recorded their findings (panel D). The three images show what the colony looked like before flooding with water (“in air” ; left panel), 4 minutes after being submerged in water (“submerged”; center panel), and 25 minutes after being submerged in water (“submerged”; right panel). Having observed the life cycle, they constructed a model schematic of the life cycle for the Jeongeupia sacculi sp. nov. HS-3 colonies (panel E).

Colony morphology and model of colony growth.
Figure 4. “Internally growing cells and crowding out. … (D) Time-lapse images of a mature colony in air (left panel) and after being submerged in water (middle and right panels). The arrow indicates the waterborne coccobacillus cells released from the colony. The colonies were grown for 5 days on agar before the time-lapse analysis. The time (min) after chase is shown. Bars = 100 µm. The original video is available as Video 3. (E) Illustration of the potential multicellular life-cycle of HS-3. (I) Coccobacillus cells attached to a new solid surface. (II) The cells proliferate to some extent, generating a liquid-crystal texture. (III) The center area becomes raised due to clustering of internal cells, leading to the germ-like phase. (IV) A waterflow releases coccobacilli. (V) In the absence of a waterflow, outward growth of the internal coccobacillus cells results in ‘crowding out’.” (Mizuno et al. 2022, cropped to panels D and E).

7.2.2. Questions

  1. Which panels show data that would be equivalent to the cave flooding for the organism?  [pick all that apply]
    1. left panel
    2. center panel
    3. right panel
    4. none of the panels
  2. What feature is indicated by the arrow in the microscopy images (panel D)?
    1. The edge of the multicellular colony
    2. The agar plate injection site
    3. The release of cells from the cell mass
    4. The water injection site into the colony
  3. Where in the life cycle diagram is the “arrow feature” depicted (panel E)?
    1. Attachment
    2. Liquid crystal phase
    3. Germ-like phase
    4. Crowding Out
    5. Releasing into water
    6. Crowding out
  4. What is happening to the cells at the crowding out stage (panel E)?
    1. The growth of HS-3 cells into a multicellular, differentiated colony
    2. The release of cells from the center of the multicellular mass
    3. The growth of cells in the colony after coccobacillus cells are released
    4. The attachment of cells to the surface and sides of the agar dish
  5. Why is it significant that the bacteria have life stage four (IV; panel E)?
    1. The organism grows on crystals submerged  in water.
    2. The behavior of the organism matches the natural habitat.
    3. The organism can tolerate high pressure under water.
    4. The natural habitat of the organism is frequently dehydrated.
  6. Lab conditions are not always true depictions of what happens in nature. So, it would be good to compare them. Which of the following would be a good way to determine if cells released during the life cycle lab experiment differ from cells released in the natural environment?
    1. Microscopically compare cells released in the cave water after flooding to cells released after plate flooding.
    2. Microscopically compare cells on the plate before flooding and to cells present on the plate after flooding.
    3. Microscopically compare cells in the cave before flooding and to cells present in the cave after flooding.
    4. Microscopically compare cells in the cave before flooding and to cells present on the plate before flooding.

8. Paper Information and Licensing

8.1. Snippet paper

  • Mora C, McKenzie T, Gaw IM, Dean JM, von Hammerstein H, Knudson TA, Setter RO, Smith CZ, Webster KM, Patz JA, Franklin EC. 2022. Over half of known human pathogenic diseases can be aggravated by climate change. Nature Climate Change. 12(9):869–875. https://rdcu.be/ePoTW
  • This article is not licensed for Creative Commons use; see copyright information. Thus, the abstract and figures cannot be copied here.

8.2. Main paper

License

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Podcast Annotation and Resources in Microbiology Copyright © 2025 by Rebecca Seipelt-Thiemann; Nancy Boury; Gwendowlyn S. Knapp; Amaya Garcia Costas; and Patrick Armstrong is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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