Genome sequence analysis and Lactobacillus paragasseri-Erakina

Lactobacillus paragasseri is closely related to the bacterial species Lactobacillus gasseri which is probiotic.

Probiotics: An introduction

Probiotics are beneficial or good bacteria that form symbiotic relationships with their hosts. These bacteria bestow several benefits which are as follows-

  • They improve digestion and maintain the pH of the gastrointestinal tract.
  • They protect the urogenital tract from certain infections as they possess antimicrobial properties.
  • These bacteria also boost the intensity of the body’s immune response.
  • They protect the body from several microbes and pathogens.

Probiotics are usually consumed as a dietary supplement but several probiotic-rich foods can be consumed daily, such as-

  • Foods that have been fermented.
  • Yoghurt 
  • Curd 
  • Cheese 

Probiotics provide several benefits including reducing inflammation and protection against pathogens. It is imperative to make probiotics a part of one’s diet to stay healthy and improve one’s immunity. Probiotics are also widely used for weight loss and hence, play a role in mitigating the effects of obesity.

Probiotic-rich food
Foods that possess natural probiotics.

Genus Lactobacillus and its features

Bacterial species belonging to the genus Lactobacillus are present ubiquitously in the bodies of both humans and animals. These bacteria make up a large part of the natural flora of the gastrointestinal and urogenital tracts of most animals. In ruminant animals, these bacteria help in the reduction of complex starch molecules into simple starch molecules within the rumen.

In humans, these bacteria act as probiotics and provide various health benefits. They are naturally-occurring bacteria and act as commensals. They form symbiotic relationships with their hosts. They are not parasitic and have not been known to cause any detrimental effects to their hosts. 

Physiology and morphology 

The physiological and morphological features which make Lactobacillus species different from other bacterial species are as follows-

  • They are rod-shaped and do not form spores.
  • They are facultative anaerobes; their metabolism does not stop even in the absence of oxygen.
  • They are Gram-positive. They have a thick outer peptidoglycan layer and lack an outer lipid layer.
  • They are catalase-negative; they do not employ the use of oxygen as a terminal electron acceptor during the process of respiration.
  • They produce lactic acid as a result of carbohydrate fermentation, hence the name ‘Lactobacillus’.
  • These bacterial species are present singly or in pairs when observed as colonies.[Lactobacillus paragasseri]

Colony characteristics 

When grown under optimal conditions on a suitable nutrient medium such as MRS agar, Lactobacilli exhibit the following colony characteristics-

  • The colony sizes range between 2 mm and 5 mm.
  • The colours of the colonies range from white to brown. 
  • Colonies are usually circular with irregular edges.[Lactobacillus paragasseri]
  • The edges of the colonies are umbonate meaning they have a protrusion along the edges.
  • The texture of the colonies is usually rough.
  • The profile of the colonies is raised in the shape of a convex.
  • Colonies are usually opaque or translucent in appearance.
Lactobacillus rhamnosus  Lactobacillus paragasseri
SEM image of a species of Lactobacillus.

Lactobacillus paragasseri: An introduction

Lactobacillus gasseri is a probiotic bacterium that is commonly used for weight loss. It is also known to prevent the incidence of infections in the urogenital tracts of women. It is a part of the normal microbiota of the urogenital and reproductive tracts in women.[Lactobacillus paragasseri] This species of bacteria are known to protect the body against the following infections and diseases-

  • Ulcerative colitis 
  • Endometrial pain
  • Irritable Bowel Syndrome 
  • Peptic ulcers 
  • Bacterial vaginosis

This bacterial species suppresses harmful microbes such as pathogenic bacteria and fungi. Studies have also shown that this bacterium increases weight loss by approximately 9%.

Probiotics Lactobacillus paragasseri
SEM of Lactobacillus gasseri.

Lactobacillus paragasseri is the sister taxon of Lactobacillus gasseri. This novel bacterial strain was identified along with two other bacterial strains that were initially thought to be Lactobacillus gasseri itself.[Lactobacillus paragasseri]

However, after whole-genome sequence analysis and phylogenetic studies that also included the polyphasic taxonomic approach, it was concluded that this bacterial strain is an entirely separate species that is closely related to Lactobacillus gasseri.

Physiology and morphology 

The physiological and morphological characteristics of Lactobacillus paragasseri are very similar to most Lactobacillus species.[Lactobacillus paragasseri] These characteristics are as follows-

  • They are rod-shaped.
  • They do not form spores.
  • They are homofermentative in nature. 
  • They are facultative anaerobes.
  • They are Gram-positive bacteria. 
  • They are catalase-negative. 
  • These bacteria are non-motile.

Optimal growth conditions

It is important to note that the novel bacterial strain grew optimally under the following conditions-

  • They grew optimally at room temperature. 
  • The agar plates need to be incubated in low pH conditions to induce optimal growth of the bacterial colonies. 
  • The nutrient medium should contain 2.0% of NaCl (Sodium chloride, w/v)


Lactobacillus paragasseri is a novel bacterial strain that has been identified as a sister taxon of the probiotic bacteria Lactobacillus gasseri via various phylogenetic studies and genome sequencing methods. The probiotic nature of this novel bacterial strain is yet to be fully studied. It exhibits all the physiological, morphological and colony characteristics of most Lactobacillus species.

Internal links:

Lactobacillus rodentium – Erakina

The starter bacterium (Lactobacillus delbrueckii)-Erakina

The racehorse bacterium (Lactobacillus equicursoris)-Erakina

External links:

Read more about Probiotics bacteria

By Deepika Thilakan

Date: 29/06/2022

Tags: life science

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