What is the Difference Between Bacillus Subtilis and Bacillus Cereus

The main difference between Bacillus subtilis and Bacillus cereus is that Bacillus subtilis is an obligate aerobe that occurs in diverse environments, both aquatic and terrestrial, whereas Bacillus cereus is a facultative anaerobe that causes foodborne illnesses in humans and animals.

Bacillus subtilis and Bacillus cereus are two types of Bacillus species that are Gram-positive and rod-shaped. They form protective endospores in order to tolerate extreme environmental conditions.

Key Areas Covered

1. What are Bacillus Subtilis
     – Definition, Features, Importance
2. What are Bacillus Cereus
     – Definition, Features, Importance
3. Similarities Between Bacillus Subtilis and Bacillus Cereus
     – Outline of Common Features
4. Difference Between Bacillus Subtilis and Bacillus Cereus
     – Comparison of Key Differences

Key Terms

Bacillus Cereus, Bacillus Subtilis

What is Bacillus Subtilis

Bacillus subtilis is a Bacillus species that is also known as hay bacillus and grass bacillus. It is a Gram-positive bacterium and it is catalase-positive. In general, it occurs in the soil and the gastrointestinal tracts of humans, animals, and marine sponges. Normally, Bacillus subtilis occurs in the upper layer of soil. In humans, it occurs as a normal gut commensal. Moreover, soil contains 10⁶ spores per gram while human feces contains 10⁴ spores per gram. The main importance of the endospores of Bacillus subtilis is that it allows the bacterium to remain viable for decades.

Figure 1: Bacillus subtilis

Furthermore, endospores tolerate salinity, drought, radiation, extreme pH, and solvents. The formation of endospores of Bacillus subtilis occurs at times of nutritional stress using hydrolysis. Generally, Bacillus subtilis is rod-shaped and forms tough, protective endospore that allows the bacterium to tolerate extreme environmental conditions. The most significant feature of Bacillus subtilis is its respiratory mode. Generally, it is an obligate aerobe.

What is Bacillus Cereus

Bacillus cereus is another species of Bacillus species that is Gram-positive and rod-shaped. The bacterium occurs in the soil, food, and marine sponges. In general, some strains of Bacillus cereus are harmful and cause foodborne illnesses. Bacillus cereus cause illnesses due to their spore-forming nature. Meanwhile, other strains show mutualism with certain plants. Some are beneficial as probiotics. However, the main importance of endospores of Bacillus cereus is their ability to tolerate unfavorable environmental conditions.

Figure 2: Bacillus cereus

Moreover, Bacillus cereus is a facultative anaerobic bacterium that has numerous virulence factors. Some of the virulence factors include phospholipase C, sphingomyelinase, cereulide, and metalloproteases. On the other hand, the strains of Bacillus cereus are mesophilic and therefore, the optimal temperature of the bacterium is 25 °C and 37 °C. They are neutralophilic and therefore, the optimal pH of Bacillus cereus is neutral pH. Generally, another importance of Bacillus cereus is the formation of biofilms. This bacterium presents a large challenge to the food industry due to its capability to contaminate food.      

Similarities Between Bacillus Subtilis and Bacillus Cereus

• Bacillus subtilis and Bacillus cereus are two types of Gram-positive bacteria that belong to the genus Bacillus.
• Both are rod-shaped bacteria.
• Both occur in soil.
• They produce protective endospores in order to tolerate harsh environmental conditions.
• They exhibit flagella-motility.

Difference Between Bacillus Subtilis and Bacillus Cereus

Definition

Bacillus subtilis refers to a Gram-positive, catalase-positive bacterium that occurs in the soil and gastrointestinal tract of ruminants, humans, and marine sponges while Bacillus cereus refers to a Gram-positive, rod-shaped bacterium, commonly found in soil, food, and marine sponges.

Occurrence

Bacillus subtilis occurs in diverse environments including aquatic and terrestrial habitats and the gastrointestinal tracts of animals while Bacillus cereus occurs in soil, food, and marine sponges.

Respiratory Method

Bacillus subtilis is an obligate aerobe while Bacillus cereus is a facultative anaerobe.

Importance

Bacillus subtilis forms biofilms while Bacillus cereus causes foodborne illnesses.

Conclusion                                                      

In brief, Bacillus subtilis and Bacillus cereus are two types of Bacillus species. They are Gram-positive bacteria that are rod-shaped. In addition, they contain flagella. Generally, both produce protective endospores to tolerate harsh environmental conditions. Generally, Bacillus subtilis occur in diverse environments including terrestrial and aquatic habitats and inside the gastrointestinal tract of humans and animals. It is an obligate aerobe. In comparison, Bacillus cereus is a facultative anaerobe that occurs in soil, food, and marine sponges. Therefore, the main difference between Bacillus subtilis and Bacillus cereus is their mode of respiration.             

References:                

1. Earl AM, Losick R, Kolter R. Ecology and genomics of Bacillus subtilis. Trends Microbiol. 2008 Jun;16(6):269-75. doi: 10.1016/j.tim.2008.03.004. Epub 2008 May 28. PMID: 18467096; PMCID: PMC2819312.
2. Bacillus cereus. BC Centre for Disease Control.

Image Courtesy:

1. “Bacillus subtilis Spore” By Y tambe – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Bacillus cereus endospore stain” By T. Nims – Own Work (CC BY-SA 4.0) via Commons Wikimedia