Introduction 

Lactobacillus gasseri is a probiotic bacteria belonging to the Lactobacillus genre found in the gastrointestinal tract and the female genital areas.

The Lactobacillus species are known as good bacteria that have probiotic properties found in the bodies of humans and animals. This type of bacteria is located in the gastrointestinal tract of humans and animals, including bees. Furthermore, Lactobacillus species are found in the female genital areas. Lactobacillus is responsible for protecting the gastrointestinal tract from harmful pathogens, maintaining the microbiome in the body, regulating immunomodulation, and improving nutrient absorption. Lactobacillus gasseri is found in the vaginal secretions, the digestive system, and breast milk. This bacteria has a significant influence on weight loss as it has been an inhibitor of obesity and diabetes. Therefore, these lactobacillus species are utilized in the food and pharmaceutical industries as they are available in medications.

An Overview of Lactobacillus gasseri

Lactobacillus gasseri is a facultatively anaerobic, rod-shaped, non-motile, non-sporulating, gram-positive bacteria that does not contain catalase to convert hydrogen peroxide (H2O2) into oxygen and water. They are homofermentative as they produce lactic acid on metabolizing glucose. The colonies were cream-colored and were found to grow optimally at 37°C with a pH of 1.5–2 after incubating in MRS agar for 24–48 hours. The GC content was recorded to be 35.3 mol%.

Lactobacillus gasseri has been located in the gastrointestinal tract, vagina, and oral cavity. Therefore, the properties of this bacterial species have been found to contain several health benefits by improving the immune system and suppressing harmful pathogens. Other health benefits include maintaining the vaginal and intestinal flora and preventing diseases like bacterial vaginosis, peptic ulcers, irritable bowel syndrome, endometrial pain, etc. Lactobacillus gasseri is accompanied by other lactobacillus species to provide these benefits to human health.

Functions and Benefits

Lactobacillus gasseri is responsible for maintaining gut homeostasis. This helps decrease the gastrointestinal (GI) transit time, regulate the metabolic rate in the host, and improve the inner epithelial barrier in the GI tract. Treatment of constipated patients with it has been found to have consistent feces volume and improve digestive functions of the GI tract, thus improving gut health in humans. Consumption of yogurt fermented with probiotic bacteria such as Lactobacillus gasseri has been observed to increase IgA secretion (immunoglobulin A-blood protein antibody part of the immune system) in the intestinal mucosal layer. This has been shown to reduce fecal cytotoxicity, thereby reducing Salmonella choleraesuis pathogens that are found adhered to the intestinal layer. Helicobacter pylori, a gastric pathogen responsible for causing gastric infections, is observed to be inhibited by Lactobacillus gasseri. Therefore, studies have shown that Lactobacillus gasseri significantly improves gut health and reduces any plausible disease-causing pathogens. Additionally, the putative pathway for metabolizing oxalate (a toxic compound in some foods) assists in regulating kidney homeostasis. Furthermore, it has been found to inhibit the development of HCl-induced lesions in the GI tract, thereby healing these lesions. 

The microbiota of the vagina consists of a significantly reduced population of Lactobacillus species. However, they are dependent on race, physiological time, and state. In addition, Lactobacillus gasseri has been found to have occupied a majority of the lactobacillus species in the healthy female vagina. These bacteria can resist the colonization of pathogens by making the conditions unfavorable for the pathogens to grow. It also produces lactic acid, which is responsible for causing an acidic pH environment in the vagina, thereby making it difficult for the harmful microbes to grow. The pathogens do not grow efficiently under lower pH. Furthermore, this lactobacillus species produces hydrogen peroxide and bacteriocins that inhibit the pathogens from adhering to the mucosal layer in the vagina. Lactobacillus gasseri has also been shown to be antimicrobial against Prevotella bivia (which causes pelvic inflammation) and Gardneralla vaginalis (which causes bacterial vaginosis), thereby preserving vaginal homeostasis.

Probiotic bacteria can modulate the immune system by determining the microorganism-associated molecular patterns (MAMPs) with the help of pattern recognition receptors (PRRs) on cells that present antigens. Lactobacillus gasseri can interact with specific toll-like receptors (TLRs) on the macrophages that sense the molecular patterns of the pathogens to commence the innate immune response. As part of immune signaling, the glycolipids, lipoteichoic acids, and peptidoglycan compounds of Lactobacillus gasseri are activated. Therefore, this bacteria plays a vital role in initiating innate immune responses to foreign pathogens, thereby aiding immunomodulation. 

Numerous studies on Lactobacillus gasseri have been carried out to determine their benefits for human health and have found multiple health benefits. A few studies have shown the consumption of probiotic fermented products, especially those containing Lactobacillus gasseri, helps reduce body weight through fat loss by around 8.2–8.5% over 12 weeks. This bacteria is utilized in the pharmaceutical industry to manufacture tablets and pills. Furthermore, they are also used in the fermentation of yogurt and other dairy items as probiotic products. Therefore, Lactobacillus gasseri is consumed to replenish the lost lactobacillus species.