Human Insulin Modulation of Escherichia coli Adherence and Chemotaxis

Abstract

Escherichia coli exhibited increased hydrophobicity and mannose-resistant epithelial cell adherence after growth in the presence of human insulin (2 µU mL¯1 or 200 µUmL¯1 insulin, respectively) with glucose (100 mg dL¯1). Capsule production and hemagglutination were unaffected by insulin and glucose. Chemotactic attraction to glucose as compared to insulin or glucose alone was enhanced by the presence of insulin. Insulin alone (200 µU mL¯1) was a chemorepellent and inhibited flagellar tethering to glass. These findings indicate that human insulin can modulate E. coli's expression of factors associated with pathogenesis in a manner that is modifiable by the presence of glucose.

Effect of Human Insulin on the Formation of Catheter-Associated <i>E. coli</i> Biofilms

“…In E. coli, insulin-rquorum signaling has been shown in previous studies to play an important role in the regulation of E. coli chemotactic responses, growth rates, and biofilm formation [24] [25]. In the presence of glucose, insulin-r enhances E. coli biofilm formation [25]. However, whether insulin and glucose affect biofilm formation under oxygen limitation (anoxic conditions) is not known.…”

“…Previous studies show that insulin together with glucose enhances E. coli surface hydrophobicity [25]. To determine if E. coli association with silicon catheter segments is related to insulin-mediated changes in E. coli surface electronegativity, the adherence to glass (silicon), a negatively charged surface, was measured under various environmental conditions (Figure 3) [29] [30].…”

“…coli ATCC 25922, a highly stable quality control strain shown to recognize and respond to insulin-r as a quorum-signaling compound, was used for all studies [24] [25]. Bacterial stock was maintained in skim milk medium at −80˚C until use.…”

“…Human recombinant insulin (insulin-r) functions as an inter-kingdom quorum-signal compound for E. coli [24] [25]. In E. coli, insulin-rquorum signaling has been shown in previous studies to play an important role in the regulation of E. coli chemotactic responses, growth rates, and biofilm formation [24] [25]. In the presence of glucose, insulin-r enhances E. coli biofilm formation [25].…”

“…The molecules that are utilized as quorum signals can be intra-species, inter-species, or inter-kingdom in origin [22] [23]. Human recombinant insulin (insulin-r) functions as an inter-kingdom quorum-signal compound for E. coli [24] [25]. In E. coli, insulin-rquorum signaling has been shown in previous studies to play an important role in the regulation of E. coli chemotactic responses, growth rates, and biofilm formation [24] [25].…”