Flow cytometry and other techniques show that Staphylococcus aureus undergoes significant physiological changes in the early stages of surface-attached culture

Abstract

The techniques of flow cytometry, scanning and transmission electron microscopy, and confocal scanning laser microscopy were used to study the physiology of Staphy/ococcus aureus in the early stages of surface-attached culture, and to make direct comparisons with planktonic bacteria grown under the same conditions. Attached bacteria growing in nutrient-rich batch culture were found to go through the same growth phases as equivalent planktonic cultures, but with an exponential growth rate of about half that of the planktonic bacteria. Viability of attached bacteria was very high (around 100°/~) throughout the first 24 h of growth. The size and protein content of attached bacteria varied with growth phase, and both measurements were always smaller than in planktonic bacteria at equivalent growth phases. Respiratory activity per bacterium, as measured by flow cytofluorimetry, and corrected for cell volume, peaked very early in attached cultures (before the first cell division) and declined from then on, whereas in planktonic bacteria it peaked in late exponential phase. Attached and planktonic bacteria showed thicker cell walls in stationary phase than in exponential phase. Membrane potentials of planktonic and attached bacteria were similar in stationary phase, but were much lower in exponential-phase attached cells than in the equivalent planktonic cells. It is apparent that a range of significant physiological adaptations occur during the early phases of attached growth.

Wavelength-normalized spectroscopic analysis of Staphylococcus aureus and Pseudomonas aeruginosa growth rates

“…Doubling times were as follows: 22.42 ± 2.1 minutes for LAC91, 33.44 ± 3.0 minutes for KH38, 37.98 ± 5.4 minutes for HH49, 24.92 ± 1.8 minutes for HH36, and 157.17 ± 19.4 minutes for PA01. S. aureus has previously reported doubling times of between 24 and 57 minutes [32][33][34], while P. aeruginosa has reported doubling times of between 100 and 200 minutes [35,36]. Therefore, there is excellent agreement between the current results and previous results in the field.…”

Interactions between Biocide Cationic Agents and Bacterial Biofilms

“…Attached S. aureus cells growing in nutrient-rich batch culture were found to go through the same growth phases as equivalent planktonic cultures and to possess high levels of viability (39). Biofilm formation in S. aureus is not as well defined as that in gram-negative bacteria and coagulase-negative staphylococci (Staphylococcus epidermidis) (25).…”

“…Such infections are characteristically resistant to antibiotics as well as to host defenses (7,16). Many in vitro (2,36,39) and in vivo (35) studies have attributed the resistance to the biofilm's mode of growth (slow growth rate, adhesion steps), but it is now thought that there are a number of contributory factors. The exopolysaccharide (EPS) matrix may exclude and/or influence the penetration of antimicrobial agents (11,30).…”

TLR8 Senses Staphylococcus aureus RNA in Human Primary Monocytes and Macrophages and Induces IFN-β Production via a TAK1–IKKβ–IRF5 Signaling Pathway

“…The maximum levels of IFN-b produced in response to HK S. aureus exceeded that of HK E. coli and LPS. A more potent induction of IFN-b by HK S. aureus from the exponential phase than the stationary phase may be related to the change in cell wall thickness (38), or it could reflect changes in the amount of stimulatory RNA. Only a fraction (e.g., 20-30%) of the monocyte population stained positive for IRF5 and IRF3 nuclear accumulation after TLR8 or TLR4 activation, respectively.…”