The world of microorganisms is diverse, with bacteria playing varied roles. Among these is the genus Weissella, frequently encountered in natural and human-influenced ecosystems. These bacteria are gaining attention for their multifaceted impact, from contributing to fermented foods to their presence within biological systems. Weissella exhibits a complex interplay of beneficial attributes and occasional concerns.
Understanding Weissella
Weissella is a genus of bacteria classified within the Lactobacillaceae family, part of the lactic acid bacteria (LAB) group. These bacteria were first identified and named in 1993 by Collins and colleagues, who distinguished them from other similar microorganisms. The genus was named after German microbiologist Norbert Weiss, who contributed to LAB taxonomy.
Weissella species are Gram-positive, meaning they retain a purple stain in a laboratory test due to their cell wall structure. They are facultatively anaerobic, indicating they can grow with or without oxygen, and do not form spores. Their morphology ranges from spherical or ovoid cells to irregular or short rod shapes. A defining characteristic of Weissella is its role in lactic acid fermentation, where it metabolizes carbohydrates to produce lactic acid.
Where Weissella Resides
Weissella species are widespread, found in various nutrient-rich environments. They are frequently isolated from fermented food products, including European sourdoughs, Asian and African traditional fermented foods, and fermented vegetables like kimchi.
Beyond fermented foods, Weissella is found in the microbiota of animals and humans, isolated from animal skin, milk, and feces, and from human saliva, breast milk, feces, and the vagina. These bacteria also occur on plant surfaces and in agricultural products like corn silage and forage rice.
Beneficial Aspects of Weissella
The contributions of Weissella species to food fermentation are notable, particularly their role in producing lactic acid. This acid helps preserve foods by lowering pH, which inhibits the growth of spoilage microorganisms and undesirable bacteria. The fermentation process also contributes to the distinctive flavors, aromas, and textures of various products. For instance, W. cibaria and W. confusa are known for their ability to produce exopolysaccharides, which are beneficial for the texture of fermented foods and can act as prebiotics.
Beyond their role in food, certain Weissella strains exhibit probiotic potential. Research suggests that some strains, notably W. cibaria and W. confusa, could modulate gut microbiota composition and support immune function. These bacteria can produce antimicrobial substances, such as bacteriocins, which may inhibit the growth of certain pathogens. Studies have also indicated that W. cibaria might help in oral health by inhibiting biofilm formation by Streptococcus mutans, a bacterium associated with tooth decay.
Potential Concerns with Weissella
While generally regarded as safe, certain Weissella species can occasionally act as spoilage organisms in specific food products. Their metabolic activities can lead to undesirable changes in flavor, odor, or texture, particularly in products like beer, meat, and seafood. For example, W. viridescens, W. cibaria, and W. confusa have been identified in such spoilage incidents.
In rare instances, Weissella species can behave as opportunistic pathogens, primarily affecting individuals with compromised immune systems. Cases of infection, though uncommon, have been reported, including bacteremia and endocarditis. W. confusa has been linked to sepsis and other serious infections in humans and animals. While some Weissella strains possess potential virulence factors, their role in causing disease is not fully established, and infections are treatable with common antibiotics.