RNA Arbitrarily Primed PCR and Fourier Transform Infrared Spectroscopy Reveal Plasticity in the Acid Tolerance Response ofStreptococcus macedonicus

Abstract

We have previously reported that an acid tolerance response (ATR) can be induced in Streptococcus macedonicus cells at mid-log phase after autoacidification, transient exposure to acidic pH, or acid habituation, as well as at stationary phase. Here, we compared the transcriptional profiles of these epigenetic phenotypes, by RNA arbitrarily primed PCR (RAP-PCR), and their whole-cell chemical compositions, by Fourier transform infrared spectroscopy (FT-IR). RAP-PCR fingerprints revealed significant differences among the phenotypes, indicating that gene expression during the ATR is influenced not only by the growth phase but also by the treatments employed to induce the response. The genes coding for the mannose-specific IID component, the 1,2-diacylglycerol 3-glucosyltransferase, the 3-oxoacyl-acyl carrier protein, the large subunit of carbamoylphosphate synthase, and a hypothetical protein were found to be induced at least under some of the acidadapting conditions. Furthermore, principal component analysis of the second-derivative-transformed FT-IR spectra segregated S. macedonicus phenotypes individually in all spectral regions that are characteristic for major cellular constituents like the polysaccharides of the cell wall, fatty acids of the cell membrane, proteins, and other compounds that absorb in these regions. These findings provide evidence for major changes in cellular composition due to acid adaptation that were clearly different to some extent among the phenotypes. Overall, our data demonstrate the plasticity in the ATR of S. macedonicus, which reflects the inherent ability of the bacterium to adjust the response to the distinctiveness of the imposed stress condition, probably to maximize its adaptability.The stress physiology of lactic acid bacteria (LAB) has been the target of rigorous investigation in recent years because it reveals the ability of strains to withstand and perform under the fluctuating and harsh conditions of food processes (9, 40). Among the stresses faced by LAB, acid stress is probably the most prominent, as such bacteria continuously acidify their surrounding environment by fermenting carbohydrates into acidic end products (33). Robustness under low-pH conditions is a desirable asset for industrial strains, to ensure their incessant contribution in the fermentation process that would otherwise be abrogated by this self-imposed stress (40). Aciduricity is also necessary for the survival of a strain during its transition through the digestive tract, after consumption, to exert its probiotic effects, if any (25).Within acid stress physiology, a feature of LAB that has attracted much attention is their ability to develop an acid tolerance response (ATR) (40). The ATR reflects the inherent ability of a bacterium to adapt to a sudden drop in extracellular pH. The experimental setup most commonly used to demonstrate and quantify the ATR of a strain is the following: cells are either transiently exposed to or continuously cultivated at a suboptimal acidic pH value and then acid challeng...

Incidence of Bacteriocins Produced by Food-Related Lactic Acid Bacteria Active towards Oral Pathogens

“…Differences observed in all spectral regions were more discernible after second derivative transformation (Figure 3) as expected according to previous studies [28,29]. …”

“…After 2 h of incubation, cells were collected by centrifugation, washed twice with PBS (pH 7.2) and resuspended in 30 μL of sterile double-distilled water. FT-IR sample preparation and measurements were performed according to the methodology described before [28]. In brief, 10 μL of the resulting suspension were spotted at the center of an IR transparent ZnSe optical disc.…”

Lactobacillus casei loaded Soy Protein-Alginate Microparticles prepared by Spray-Drying

“…Generally, the FTIR--ATR spectrum of L. casei 01 before encapsulation was comparable to the spectra reported for other lactic acid bacteria, identified by the FTIR fingerprint method (39,40). As in previous studies, in which emulsion and spray drying were used for microencapsulation, the spectra of non-encapsulated and L. casei 01 released from the SPI-alginate microparticles were almost identical, with an additional band at 1127 cm -1 in the spectrum of released cells relevant for lactic acid (14,16).…”

Application of Mid-infrared and Raman Spectroscopy to the Study of Bacteria

“…The authors also observed increased Raman intensity for lipids and some proteins but not for nucleic acids as a function of nanoparticle concentration indicating that nanoparticleinduced injury is likely caused by a different mechanism than antibiotic treatment in which protein and nucleic acid synthesis are inhibited. In other studies, FT-IR was used to study heat-induced lethal and sublethal injuries in Lactococcus lactis (Kilimann et al 2006), osmotic and thermally induced injuries of E. coli (Mille et al 2002), UV radiationinduced injury of Staphylococcus aureus (Krishnamurthy et al 2010), lethal injury in E. coli caused by dehydration (Beney et al 2004), radical-induced damage of Micrococcus luteus (Lorin-Latxague and Melin 2005), acid tolerance response of Streptococcus macedonicus (Papadimitriou et al 2008), and toxicity response of yeast (Corte et al 2010). Recently, the membrane phase behavior of E. coli during desiccation and rehydration was also studied by FT-IR (Scherber et al 2009).…”