Insulin Regulation of Escherichia coli Abiotic Biofilm Formation: Effect of Nutrients and Growth Conditions

Abstract

Escherichia coli plays an important role in biofilm formation across a wide array of disease and ecological settings. Insulin can function as an adjuvant in the regulation of biofilm levels. The modulation of insulin-regulated biofilm formation by environmental conditions has not been previously described. In the present study, the effects that various environmental growth conditions and nutrients have on insulin-modulated levels of biofilm production were measured. Micropipette tips were incubated with E. coli ATCC® 25922™ in a Mueller Hinton broth (MH), or a yeast nitrogen base with 1% peptone (YNBP), which was supplemented with glucose, lactose, galactose and/or insulin (Humulin®-R). The incubation conditions included a shaking or static culture, at 23 °C or 37 °C. After incubation, the biofilm production was calculated per CFU. At 23 °C, the presence of insulin increased biofilm formation. The amount of biofilm formation was highest in glucose > galactose >> lactose, while the biofilm levels decreased in shaking cultures, except for galactose (3-fold increase; 0.1% galactose and 20 μU insulin). At 37 °C, regardless of condition, there was more biofilm formation/CFU under static conditions in YNBP than in MH, except for the MH containing galactose. E. coli biofilm formation is influenced by aeration, temperature, and insulin concentration in combination with the available sugars.

Enterobacterales Biofilm-Specific Genes and Antimicrobial and Anti-Inflammatory Biomarkers in the Blood of Patients with Ischemic Heart Disease

“…Possibly, the increase in the bacterial count of some specific genera might be related to the use of antidiabetic drugs, as E. coli proliferation is increased due to insulin administration under in vitro conditions. Insulin may serve as a signal molecule for the formation of bacterial biofilms [ 50 , 51 ]. About 17% of the study patients had Enterobacterales genes in their blood: 13.3% had the gene wcaF , followed by 8% with the gene sdhC .…”

The Role of the Insulin/Glucose Ratio in the Regulation of Pathogen Biofilm Formation

“…Insulin is a phylogenetically ancient protein not only synthesized across the taxonomic kingdoms but regardless of which source, exhibits cross-kingdom activity [13][14][15][16][34][35][36][37][38][39]. Although E. coli has been demonstrated to synthesize its own insulin, as well as respond to human insulin, it has only been recently that its role as a behavioral modifier in E. coli phenotypic expression regulation has been described [10,17]. Insulin can function as an interkingdom quorum signaling compound that affects the expression of biofilm formation in E. coli in a manner that is nutrient and environmentally sensitive [17,[40][41][42][43].…”

“…For K. pneumoniae ATCC 27736, a stable highly characterized encapsulated isolate used for antibiotic testing, capsule levels were also determined in duplicate plates stained with Alcian blue, a stain specific for acidic polysaccharides, (1% w/v PBS, 30 min, room temperature) [17,20,21]. The stain was dissolved in 300 µL/well pyridine (Sigma-Aldrich, St. Louis, MO, USA).…”

“…With respect to procaryotes, LeRoith, et al [16] demonstrated that wild-type E. coli elaborates a native insulin with properties similar to mammalian insulin with respect to structure and function in a mammalian liver cell assay system. One function that insulin exhibits in E. coli is that of a rheostat, with respect to the expression of microbial phenotype regarding biofilm-forming behavior, i.e., adherence and chemotaxis, both of which appear to be dependent on the presence of carbohydrates, particularly glucose [10,17,18]. Although the administration of insulin is a mainstay in the management of the glycemic state in trauma and hospitalized patients, to date, the effect of insulin/glucose ratio over the general physiologic range on biofilm formation has not been determined.…”

Insight on Infections in Diabetic Setting

“…In fact, its anabolic effect might inhibit autophagy, thereby decreasing the antioxidant action [ 60 ], or contribute to antibiotic resistance by affecting biofilm growth. Patel et al [ 61 ] showed that while insulin alone has no effect on the level of biofilm formation or cell growth, the presence of glucose significantly enhances both. This could be a trigger for the expression of biofilm formation and UTI, particularly in the presence of external catheters.…”