Megasphaera is a genus of bacteria found in diverse environments, contributing to microbial communities in both animal and human hosts. Understanding their characteristics and activities is important for comprehending their influence on health and biological processes.
Understanding Megasphaera
Megasphaera is a genus of bacteria classified within the phylum Bacillota (Firmicutes), specifically within the class Negativicutes. These bacteria are typically gram-negative and coccus-shaped. The name “Megasphaera” refers to their large, spherical cells, which can be 1.0-2.5 micrometers in diameter.
This genus includes several species, with Megasphaera elsdenii being one of the most studied. Megasphaera species commonly inhabit the digestive tracts of animals, including the rumen of cattle and other ruminants, and the large intestine of humans. They are also found in other niches such as the human oral cavity, saliva, vaginal tract, and even in spoiled beer.
Its Functions in the Body
Megasphaera species are strictly anaerobic. Their primary function involves fermentation processes, capable of fermenting organic compounds like lactate, glucose, and other sugars.
Megasphaera elsdenii can utilize both glucose and lactate as energy sources. Through these pathways, Megasphaera produces various metabolic byproducts, including short-chain fatty acids (SCFAs) such as acetate, propionate, and particularly butyrate, along with ethanol and carbon dioxide. In the rumen of cattle, Megasphaera elsdenii consumes excess lactic acid, helping prevent a sharp drop in rumen pH and control ruminal acidosis. Some Megasphaera species can also ferment amino acids, yielding ammonia and branched-chain fatty acids that serve as growth factors for other bacteria.
Megasphaera’s Impact on Health
Megasphaera’s presence and activity influence health in various ways, with research continually exploring its complex roles. In the gut, Megasphaera species produce short-chain fatty acids like butyrate, contributing to gut health. This is relevant in ruminants, where Megasphaera elsdenii helps maintain rumen health by mitigating lactic acid buildup.
Conversely, Megasphaera has been associated with certain health conditions, especially in humans. Specific phylotypes, such as Megasphaera phylotype 1 (MP1) and MP2, are strongly linked to bacterial vaginosis (BV), a common imbalance of the vaginal microbiome. Their presence has also been noted in periodontal diseases and intra-amniotic infections.
Studies have linked Megasphaera to conditions like cervical dysplasia, dental caries, and an increased risk for HIV acquisition. A lower abundance of Megasphaera in stool microbiota has been negatively associated with diarrheal cryptosporidiosis, suggesting a potential protective role. Megasphaera elsdenii has also been correlated with elevated gas production during human gut fermentation.
Influencing Megasphaera Levels
The levels of Megasphaera within the body can be influenced by various environmental and host factors. Diet is a significant factor shaping the overall gut microbiota composition. For instance, high-fiber and carbohydrate-rich diets can lead to an increase in the abundance of bacteria from the Firmicutes phylum, which includes Megasphaera.
Specifically, in ruminant animals, high-grain diets are known to increase the ruminal abundance of Megasphaera elsdenii. General approaches to modulating microbiota levels can also include the use of probiotics and prebiotics. Lifestyle factors, along with medications such as antibiotics, can significantly alter the balance of the gut microbiota.