The environmental conditions of space, in combination with an in situ-like growth chamber, will produce a higher rate of genetic mutations and modifications that will result in an increase in bacterial isolates that produce antibiotics as compared to an Earth-based control. It is anticipated that there will be a statistically significant increase in the number of isolates that produce antibiotic metabolites and that these metabolites will be novel.
Why is this experiment important?
Space exploration is quickly increasing with the upcoming Artemis lunar missions and, eventually, Mars (National Aeronautics and Space Administration, 2020). But, space exploration is never limited to the just human species. A healthy human has more commensal microorganisms in and on their person than they have of their own cells (Tlaskalová-Hogenová et al., 2004). The human microflora should be just as susceptible to mutations and modifications after exposure to space conditions. A model that can be applied across environmental and commensal bacteria astronauts may encounter or introduce will be crucial to spending long durations in space. It’s important to understand how bacteria evolve in space conditions in order to understand the clinical and daily impact that opportunistic and pathogenic bacteria will have on the safety of those who live and work in this environment (Klaus & Howard, 2006). No studies have examined how genetic changes in space influence the production of antibiotic secondary metabolites. Research has primarily been limited to looking at bacteria of clinical pathogenic significance. Most studies focus on the ability of pathogens to become resistant to antibiotics and fail to explore the development of new antibiotics. We need to explore this area in a broader context to shed light on how and why this happens as a general trend.
Why use soil?
The most accessible and abundant reservoir of bacteria is soil. Soil is found in almost every environment where humans have established civilizations. The variety of soil bacteria is incredibly high. Soil bacteria are a prime example of a plethora of species that exist in high densities (Fierer & Jackson, 2006). Because of this, soil bacteria are excellent at evolving the ability to develop chemical metabolites to secrete into their microenvironments and
interact with surrounding microbiota and new metabolites are constantly being
created (Crits-Christoph et al., 2018; Tyc et al., 2017). Check out this soil storage study we performed to learn about how to store the soil for our experiment!
What is an ichip?
Dr. Slava Epstein of Northeastern University is the inventor of the isolation chip (ichip). The device is comprised of an array of very small through-holes that can be inoculated with roughly one cell each after the central plate is submerged in cultured, liquid agar. The array is lined with a membrane that keeps the bacteria in, but lets nutriets pass through (Nichols et al., 2010). The ichip helps fight the Great Plate Count Anomaly, which is the principle that most of the microbes present in an environmental sample cannot be cultured in isolation on a Petri dish under normal laboratory conditions (Epstein, 2013; Harwani, 2012; Staley & Konopka, 1985). The iChip provides an environment proven to be as close to in situ as is currently possible (Nichols et al., 2010). The ichip allows for a more accurate assessment of total bacterial diversity to be established. Novel bacteria can be assessed and identified which were once uncultivable (Nichols et al., 2010). This increases the likelihood of finding a truly unique chemical metabolite.
The Effect of Space on Microorganisms:
We know that the radiation and microgravity found in space cause bacteria to mutate more rapidly in off-Earth environments like the International Space Station (ISS) (Fajardo-Cavazos & Nicholson, 2016). Antibiotic resistant pathogens have already been discovered as biofilms on a variety of surfaces within the ISS (Sobisch et al., 2019). Genetic mutations can result spontaneously and as a response to a variety of environmental stressors (Schroeder et al., 2018). Stressors may include a lack of nutrients, thermal irregularity, presence of antibiotics, and DNA damage (Foster, 2007). This last idea is most relevant to space. The Earth’s magnetosphere provides adequate protection to most organisms. However, as one begins to leave this protection, the amount of interplanetary radiation increases. A multitude of high-energy radiation sources exist: solar photons, protons, electrons, and charged particles. It has been previously shown that bacteria will respond to an excess of these stressors with multiple and varying mutations (Moeller et al., 2010). Microgravity is also suspected to play a role in bacterial mutagenic modification. Earth-based and spaceflight research suggests that a link exists between gravity and bacterial metabolism (Huang et al., 2018).
Bacteria are subject to the same rules of nature that constrain all living organisms. They continuously engage in a war for survival within their natural environments and compete for resources (Hibbing, 2010). Through the millennia, they have acquired adaptations to aid in their survival. The natural process of mutations within a population allow them to develop genetic modifications to aid them in outcompeting other species of bacteria (Woese, 1987). Many of these mutations cause bacteria to produce and secrete chemical metabolites. These metabolites vary greatly from species to species and enable a bacterium to interact with its environment and other species of bacteria. In certain cases, bacteria create a chemical microenvironment around the cell which is unsuitable or dangerous to other species in order to dominate a niche in their environment (Clardy et al., 2009).
Bacteria are quick to evolve to the presence of antibiotic compounds. Due to their rapid growth and short generation time, bacteria can evolve quickly through random mutation and natural selection. According to the World Health Organization (WHO), it is estimated that antibiotic resistance will be responsible for ten million deaths each year by 2050. In 2018, the WHO declared that antibiotic resistance is “one of the biggest threats to global health, food security, and development today” (Interagency Coordination Group on Antimicrobial Resistance, 2019). Most biotech companies put little focus into early-stage research to discover novel antibiotics. Crowdsourcing through educators and student researchers can accelerate compound discovery.
The Origin of Clinical Antibiotics:
Starting with Sir Alexander Fleming’s discovery of penicillin in 1928, scientists have been able to extract substances from microbiota and harness them to manage human infections. The word “antibiotic” was first used by Selman Waksman in 1941 to describe these invaluable substances (Clardy et al., 2009). The use of antibiotics in clinical care is one of the most impactful inventions of science ever made and has contributed to saving millions of lives and increasing life expectancy around the world.