Related Experiment Video

Updated: Jun 10, 2026

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat
08:27

Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat

Published on: October 29, 2014

An ubiquitous antibacterial toxin from human gut bacteria engenders neonatal colonization advantage

Ezequiel Valguarnera1, Jessica Tung1, Jesse J Pak1

  • 1Department of Pediatrics, Washington University, St. Louis, MO, USA.

Nature Communications
|June 8, 2026
PubMed

Insights

The Type 6 Secretion System (T6SS) in Bacteroides fragilis, particularly the Bte3 toxin, plays a key role in early life gut colonization competition. This system helps strains dominate the gut environment unless competing bacteria have immunity to Bte3.

Area of Science:

  • Microbiology
  • Gut Microbiome Research
  • Bacterial Pathogenesis

Background:

  • Bacteroides fragilis is a dominant commensal in the human gut microbiome.
  • The Type 6 Secretion System (T6SS) in B. fragilis is hypothesized to mediate inter-strain competition.
  • Understanding T6SS function is crucial for comprehending gut microbial dynamics.

Purpose of the Study:

  • To characterize the T6SS toxin repertoire in clinical isolates of B. fragilis.
  • To investigate the role of the T6SS effector Bte3 in inter-strain competition during early life colonization.
  • To explore the potential of T6SS diversity in shaping the gut microbiome.

Main Methods:

  • Sequencing of nearly 900 clinical B. fragilis isolates.
  • Characterization of T6SS effector repertoire, focusing on Bte3.
  • In vitro intoxication assays with B. fragilis and Enterobacteriaceae.
  • Murine model of neonatal gut colonization using T6SS-isogenic strains.

Main Results:

  • Bte3 was identified as a prevalent T6SS effector.
  • Bte3 demonstrated intoxication of B. fragilis and Enterobacteriaceae via a novel secretion mechanism.
  • In vivo, Bte3-containing strains outcompeted susceptible B. fragilis strains in neonates.
  • Strain displacement was dependent on the target strain's immunity to Bte3.

Conclusions:

  • T6SS diversity, particularly Bte3, significantly influences B. fragilis early life colonization and competition.
  • The potency and specificity of T6SS effectors shape the gut microbial landscape.
  • This research offers insights for designing microbial interventions for neonatal gut commensal acquisition.

More Related Videos

Assessment of Intestinal Transcytosis of Neonatal Escherichia coli Bacteremia Isolates08:32

Assessment of Intestinal Transcytosis of Neonatal Escherichia coli Bacteremia Isolates

Published on: February 17, 2023

Related Concept Videos

Introduction to the Human Microbiota01:22

Introduction to the Human Microbiota

Microorganisms colonize various regions of the human body, including the mouth, nasal passages, throat, stomach, intestines, urogenital tract, and skin. The total number of microbial cells is estimated to range from 10¹³ to 10¹⁴—comparable to, or exceeding, the number of human somatic cells. This host–microbiome relationship has led to the conceptualization of humans as supraorganisms, wherein microbial communities perform vital roles in development, immunity, and disease...
Development of Human Microbiota01:30

Development of Human Microbiota

The human microbiota begins developing at birth and undergoes continual change as we age. Infancy marks a critical period of microbial sensitivity, offering a “window of opportunity” during which beneficial microbes help mature the immune system. By age three, children typically develop a more stable and diverse microbial community. Newborns acquire microbes from their immediate environment; vaginal delivery favors maternal vaginal microbes, while cesarean births favor microbes from the skin...
Development of the Oral Microbiota01:28

Development of the Oral Microbiota

The establishment of the oral microbiome begins before birth, challenging the long-held belief that the fetal oral cavity is sterile. The presence of oral microbes such as Streptococcus and Fusobacterium in amniotic fluid suggests that microbial exposure may occur in utero, potentially through translocation from the maternal oral or gastrointestinal tract. This early colonization primes the neonatal immune system and sets the stage for subsequent microbial succession. Maternal health,...
Bacterial Toxins01:12

Bacterial Toxins

Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...
Microbiota Modulation by Antibiotics01:21

Microbiota Modulation by Antibiotics

Antibiotics have revolutionized modern medicine by saving countless lives from bacterial infections. However, their widespread use has inadvertently harmed the delicate balance of the human gut microbiota. The gut microbiota, a complex community of bacteria, archaea, viruses, and fungi, plays a vital role in regulating metabolism, immune responses, and maintaining intestinal health. Antibiotics, especially broad-spectrum types, disrupt this ecosystem by eradicating both harmful and beneficial...
Transduction01:16

Transduction

Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome are...