Untitled Quiz

Normal Flora

• A diverse microbial flora is associated with the skin and mucous membranes of every human being from shortly after birth until death.
• Normal microbial flora inhabiting the human skin, nails, eyes, oropharynx, genitalia, and gastrointestinal tract are harmless in healthy individuals.
• Normal flora can cause disease in compromised hosts.
• Viruses and parasites are not considered members of the normal microbial flora in humans.
• Gene sequencing helped to identify and classify bacteria based on 16s rRNA and physicochemical properties.
• Microbes aid in nutrition, immune system and neurological development, gut maturation, and pathogen defense.
• The human body contains about 10¹³ cells, routinely harbors about 10¹⁴ bacteria.
• Normal microbial flora is relatively stable, with specific genera populating various body regions during particular periods in an individual's life.
• Microorganisms of the normal flora may aid the host, may harm the host, or may exist as commensals.
• Main factors determining the composition of the normal flora in a body region are pH, temperature, redox potential, and oxygen, water, and nutrient levels.
• Other factors include peristalsis, saliva, lysozyme secretion, and secretion of immunoglobulins.
• Local environment is like a concerto in which one principal instrument usually dominates (e.g., a Gram-positive population (bifidobacteria and lactobacilli) in breastfed infants).
• Breast milk contains unique microbiota, including beneficial, symbiotic, and potential probiotics.
• Human milk oligosaccharides (HMOs) in breast milk modulate intestinal microbiota and act as prebiotics for beneficial bacteria.
• This beneficial bacterial population is reduced and displaced by Gram-negative bacteria (Enterobacteriaceae) when the baby is bottle-fed.
• The type of liquid diet provided to the infant influences the normal flora control.
• Bovine milk is a significant substitute for human breast milk, with bioactive compounds, including microbiota derived from milk.
• Bovine milk microbiota supports early-life gut development by improving the intestinal microbiota and immune functions.
• The overall energy production and digestion within the body depends on the intactness of the resident communal flora
• Disturbances in the body's bacterial composition can cause various metabolic disorders and other health complications.
• Dominance of methanogens may cause bloating, and high-sugar feed might lead to ruminal acidosis.

Normal Delivery & C-sections

• Studies show that intestinal microbiota composition in vaginally delivered infants differs from those delivered by C-section.
• Infants delivered vaginally obtain microorganisms from the birth canal, mostly anaerobic bacteria; these form the initial infant microbiota.
• The vagina of pregnant women contains a large amount of Lactobacillus which keeps a low pH environment, inhibiting the growth of harmful bacteria.
• Microbiota of naturally delivered babies was similar to the vagina microbiota of the mother.
• During vertical transfer, the mother passes vaginal microorganisms.
• High abundance of Bifidobacteria, Bacteroides, Prevotella, and Leptothrix.
• Infants delivered by C-section have initial contact with the hospital environment and the mother's skin.
• Early intestinal microbiota in C-sections is similar to the mother's skin microbiota, with facultative anaerobes like Staphylococcus, Propionibacterium, and Corynebacterium. With a low abundance of Bacteroides and Bifidobacteria.
• Intestinal colonization by Bacteroides is delayed.
• Microbial diversity in C-section babies is lower.

Early-life respiratory tract and gut microbiome

• Early-life microbiome plays an important role in infant health.
• Factors such as mode of delivery, feeding type, and exposure to endotoxins alter the microbiome composition.
• Perturbations in the infant microbiome can affect long-term microbiota composition, possibly determining predisposition to inflammatory diseases (like severe RSV disease).

Normal Flora (Plants and Fish)

• Plant phyllosphere dominated by strict aerobes like Methylobacteriaceae and Sphingomonadaceae.
• Abundance low in plant roots, replaced by facultative anaerobes.
• Plant and fish microbiotas share common facultative anaerobes.
• Plant and fish gut microbiotas feature a thick mucus biofilm.
• Comamonadaceae, Oxalobacteraceae, Flavobacteriaceae are abundant in plant and fish mucus, especially in gill microbiota.

Microbiome Analysis Methods

• High-throughput sequencing (HTS) and analysis methods provide insights into the structures and functions of microbiomes.
• Culturome involves the targeted selection of microbes, providing microbial isolates for quick analysis.
• Amplicon (16S/18S/ITS) methods involve low-biomass requirements, taxonomic resolution to species level, and evaluation of functional potential of uncultured species.
• Metagenomics analyze the collective genomes.
• Metatranscriptomics determine active microbes by analyzing the transcriptomes.
• Metaproteomics examines the expressed proteins, while metabolomics detects the metabolites.

Germ Free Mice Models

• Gnotobiology revolutionized the study of microbiota-host interactions.
• Germ-free mice lack all microorganisms, making them valuable models for studying specific bacterial species' effects.
• GF models offer a completely blank microbial background for studying correlative and causal effects.
• Fecal microbiota transplantation (FMT) strengthens the use of GF mice in research.

FMT - Microbial Seeding

• FMT involves the administration of fecal matter from healthy donors into the recipient's intestinal tract to change and restore the microbiome.
• FMT is used to treat various inflammatory bowel diseases (IBD) like Crohn's disease and ulcerative colitis.
• FMT has been shown to suppress intestinal apoptosis, regulate lymphocytes, and increase the abundance of healthy-related microbiota in patients with irritable bowel syndrome (IBS).

Microbiome Connectivity

• Microbiome transfer occurs between environments.
• Mechanisms like vertical (e.g., placental transfer), horizontal, and via aerosols, food, water, and medical applications.

Holo-genomics

• An integrated study, considering not only the host's genomes but also those of their associated microbes, other life forms, and viruses.
• Includes microbiome interactions, metabolic collaborations, vertical inheritance, and mutual symbiosis for holobiont development.

Biomarkers for Gut Microbiota & Health

• SCFAs can be used as biomarkers for gut microbiota health.
• High SCFA levels may indicate beneficial factors related to health.
• Fecal SCFAs are good biomarkers.
• Studies examine the relationship between serum SCFAs and diseases like Multiple Sclerosis (MS).

Dietary Fiber and SCFA-producing Bacteria

• Different dietary sources are associated with specific SCFA-producing bacteria.
• Fermentable carbohydrates and resistant starches stimulate SCFA production.
• Various food types support different types of gut communities.

Gut Microbiome Homeostasis & Dysbiosis

• Gut dysbiosis is influenced by different factors and nutrition.
• Dietary changes can dramatically shift gut microbiota composition.
• Several chronic diseases may potentially be related or even caused by gut microbiome dysbiosis.

Mechanisms of Normal Flora Defense

• Components of normal flora defend against invading pathogens.
• Mechanisms include layer formation, waste product inhibition, and stimulation of the immune system.

Immune Effects of SCFAs

• SCFAs affect immune cells like macrophages, neutrophils, and T cells.
• SCFAs potentially influence the expression of anti-microbial protein cathelicidin

SCFAs as Energy Source

• SCFAs are major energy sources for colon cells, providing up to 8% of daily energy in some cases.
• SCFAs might reduce lipolysis, insulin-mediated fat accumulation, and accumulation in adipose and skeletal muscle tissues as seen in some studies.

Other topics covered:

• Various plant and animal microbiomes.
• Diverse methods of microbiome analysis.
• Specific considerations like vaginal seeding.