Indeed, studies in Escherichia coli demonstrated that Usp1 from Lb. A whole genome DNA microarray was employed to determine the transcriptional response of Lb. Differential expression of a wide variety of genes involved in cell envelope stress, protein denaturation and DNA damage was observed. Interestingly, survival of Lb. The importance of MDR transporters for the bile stress response of Lb. Indeed, of the ten most highly induced genes in Lb. These transporters function by extruding structurally unrelated compounds from the cell including antibiotics and bile salts [ 90 ]. MDR transporters were also identified in B.
Expression of the MDR transporter from B. However, the modified strain exhibited a reduced growth rate; hence the authors suggest that production of the MDR transporter is toxic for the cells. A gene responsible for S-layer production in Lb. S-layer proteins are external bacterial structures which have been associated with protection against hostile environmental elements and the establishment of Lb. However, the expression of slpA in 0. The authors therefore suggest that slpB , rather than slpA , may be expressed during unfavorable growth conditions [ 92 ].
A putative aggregation-promoting factor Apf of Lb. Moreover, adherence of stationary phase mutant cells to an intestinal epithelial cell line was reduced. Overall, the results of the study suggest that Apf-like proteins are important for the gastrointestinal robustness of Lb.
The general global cellular response of probiotic bacteria to environmental stresses can probably be grouped into six broad biological categories based on differential expression of the associated genes and on the encountered stress es : i stress response genes, ii genes involved in energy metabolism, iii transcription and translation associated genes, iv genes involved in nucleotide metabolism and amino acid biosynthesis genes, v cell envelope and cell wall-associated genes, vi genes which have no assigned function.
For example, whole genome DNA microarrays exploited to study the complete cellular response of B. The most highly and rapidly induced genes included dnaK , grpE , dnaJ and the transcriptional repressor HspR. Numerous transcriptional regulators were induced which included 2 two-component response regulators and the corresponding sensor histidine kinases. Ten LacI-type sugar-responsive-repressors were up-regulated and genes involved in the SOS response were also induced including the transcriptional repressor LexA and genes encoding RecA, RecX and RecN as well as the trans -translation machinery.
While ssrA was constitutively expressed, the gene encoding SmpB was highly induced following heat-treatment in B. An investigation into the global stress response of B. Interestingly, exposure to moderate temperatures of 42 o C and 44 o C for 1 hour resulted in the induction of 5 and 17 genes, respectively and down-regulation of 11 and 92 genes, respectively.
In contrast, genes were induced during severe heat treatment 47 o C while genes were down-regulated. Under conditions of severe heat shock, genes belonging to carbohydrate transport and metabolism, energy production and conversion and nucleotide transport and metabolism were negatively regulated. Of the up-regulated genes only a fraction were involved in protein misfolding and DNA damage. Based on the overall results, the authors proposed a model interactive regulatory gene network for the bifidobacterial stress response whereby the negative regulator HspR controls the SOS response and the ClgR regulon, which in turn is regulated by and regulates the negative regulator HrcA [ 99 , ].
Previous studies have suggested that different bifidobacteria use NADH peroxidase to prevent the accumulation of H 2 O 2 ,, , however, none of the sequenced genomes to date contain gene analogs for this enzyme. Interestingly, a recent proteomic study of the oxidative stress-related responses of B. The activity of Dps in oxidative stress protection was confirmed by in vitro and in vivo studies.
Indeed, in vitro studies revealed that Dps binds DNA to protect it from oxidative degradation and over-expression of the protein in E. Adapting Lb. Assessment of the transcriptional responses of the strain following 5 and 20 minutes of exposure to this pH revealed a dramatic increase in the number of responsive genes following the 20 minute treatment genes with altered expression levels. The majority of genes were down-regulated.
This was particularly apparent for genes involved in information storage and processing including translation, ribosomal structure and biogenesis, transcription, DNA replication, recombination and repair as well as genes involved in cellular processes such as protein turnover and remarkably stress response genes and those involved in cell secretion and cell envelope biogenesis.
Up-regulated genes included the malolactic enzyme as discussed earlier and genes involved in amino acid transport and metabolism, including those involved in the transport of histidine as previously discussed. Interestingly, genes involved in the mobile DNA elements category were also up-regulated following acid adaptation for 20 minutes. Of the poorly characterized up-regulated genes, three were associated with phospholipid turnover: an acetyl transferase, an esterase, and a putative membrane-associated phospholipid phosphatase.
Acid-adapted cells had higher total percentages of saturated and cyclopropane fatty acids in the cytoplasmic membrane than control cells which may be linked to the up-regulation of the three phospholipid-associated genes. Other studies have also demonstrated that acid stress induces changes in the cytoplasmic membrane fatty acid content in Lactobacillus [ , ]. Moreover, several stresses have been shown to cause an increase in the concentration of cyclopropane fatty acids in the cell membrane including heat stress [ ], osmotic stress [ ], and bile stress [ , ].
Indeed, using both transcriptomics and strategic proteomics approaches which also enabled a study of cell surface properties surfome Koskenniemi et al. This study also demonstrated that bile shock resulted in the repression of EPS-encoding genes. The authors postulated that EPS serves to protect Lb. However, the presence of bile serves as a signal of gut entrance and hence down-regulation in EPS production to enable better adherence of the bacterium to intestinal cells.
Genes involved in the D-alanylation of the negatively charged lipotechoic acids were also up-regulated in response to bile stress which was also observed for Lb. Such a strategy serves to increase the positive surface charge, and as the authors suggest possibly serves to repulse the cationic compounds in bile. Indeed, alteration of surface charge has also been associated with resistance to cationic peptides [ , ] and we recently observed the same phenomenon in response to bacteriophage challenge in L. Several two-component systems, multi-drug transporters, the F 1 F 0 -ATP synthase and a bile salt hydrolase were also up-regulated in response to bile stress as well as several chaperones and proteases directly involved in the stress response.
The ability of probiotic bacteria to survive the harsh environments encountered during processing and gastrointestinal transit has been a major factor in their selection criteria. Indeed, induction of the probiotic stress response through pre-adaptation strategies may not always ensure the improved performance of a strain in compromising environments. For example, exposing B. Moreover, exposure of Lb. In addition, the biological efficacy of probiotic cells may be compromised following exposure to stress. Indeed, spray drying was recently shown to negatively influence the adhesion capacity of Lactobacillus kefir but not Lb.
Indeed, we have already seen how probiotic robustness can be dramatically improved by targeting even a single mechanism. By targeting several cellular defense mechanisms in one strain we should be able to develop designer organisms with the capacity to overcome the plethora of stresses presented during processing and in vivo survival.
However, despite the advantages of using such approaches this field of science is not without its limitations. Probiotics which have been enhanced in this way are genetically modified organisms and with the exception of the United States and Canada, there is still uncertainty in the public arena towards the use of genetic manipulation. Moreover, the use of pathogen derived genes in genetically modified probiotics through patho-biotechnology is a concept that undoubtedly consumer and regulatory groups may find hard to accept.
Yet despite this, designer probiotics offer huge potential for both technological and clinical applications. Moreover, one of the major obstacles associated with genetic manipulation to date is that the benefits of the technology rarely benefit the consumer but rather serve to maximize corporate profit. Genetically modified probiotics, on the other hand, should directly benefit the consumer.
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However, studies which evaluate the safety of engineered probiotics are crucial if the technology is to gain acceptance. For this reason continued investigation and understanding of the bacterial stress response is a highly worthwhile endeavor in probiotic science providing strategies for scientists to manipulate probiotics to their full potential. In this way next-generation probiotic cultures will be better equipped to face technological and gastrointestinal challenges, which at the moment can be a rate-limiting step in probiotic selection as well as meeting medical demands.
National Center for Biotechnology Information , U. Journal List Microb Cell Fact v. Microb Cell Fact. Published online Aug Cork, Ireland Find articles by Susan Mills. Author information Article notes Copyright and License information Disclaimer. Cork, Ireland. Corresponding author. Susan Mills: ei. Conference 10th Symposium on Lactic Acid Bacterium. This article has been cited by other articles in PMC. Abstract Before a probiotic bacterium can even begin to fulfill its biological role, it must survive a battery of environmental stresses imposed during food processing and passage through the gastrointestinal tract GIT.
Introduction To suggest that probiotic bacteria have entered the realm of the highly exploited bacterial groups is an understatement. From gut… Potential probiotic cultures have been isolated from a variety of sources including animal, human and food sources. To product… In terms of processing, probiotics are commonly grown to high numbers before undergoing a drying process to produce a high-cell density probiotic powder. And back again… Passage of probiotics through the mammalian GIT is a hazardous journey, with the initial stages designed to jeopardize the survival of pathogenic microorganisms.
The probiotic stress response Bacterial cells are naturally equipped with a plethora of defense mechanisms to enhance survival in hostile environments [ 15 , 29 , 32 - 34 ]. Open in a separate window. Figure 1. Taking advantage of the bacterial stress response - genetic manipulation Exploiting probiotic stress responses It is well accepted that adaptation to a sub-lethal dose of a specific physical or chemical stress can dramatically improve subsequent performance in compromising environments and as a consequence is a popular strategy to increase both the technological and gastrointestinal robustness of a strain.
Figure 2. Exploiting stress responses of pathogenic microorganisms Patho-biotechnology is a relatively new concept which aims to exploit stress response systems of pathogenic bacteria for biotechnological and biomedical purposes [ 48 ]. Exploiting generic microbial mechanisms Improving probiotic robustness can also be achieved by looking to other microbial mechanisms which may not be necessarily associated with pathogenic survival.
Figure 3. New players involved in the probiotic stress response Proteomics and whole genome DNA microarrays alongside heterologous expression studies and the generation of deletion mutants continue to provide important insights into the response and adaptation of probiotic bacteria to environmental stresses. Holistic approaches to understanding and exploiting the probiotic stress response The general global cellular response of probiotic bacteria to environmental stresses can probably be grouped into six broad biological categories based on differential expression of the associated genes and on the encountered stress es : i stress response genes, ii genes involved in energy metabolism, iii transcription and translation associated genes, iv genes involved in nucleotide metabolism and amino acid biosynthesis genes, v cell envelope and cell wall-associated genes, vi genes which have no assigned function.
Discussion The ability of probiotic bacteria to survive the harsh environments encountered during processing and gastrointestinal transit has been a major factor in their selection criteria. Competing interests The authors declare that they have no competing interests. References Global Industry Analysts Inc. Microbial production of bioactives: from fermented Functional Foods to probiotic mechanisms.
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Modification of technical properties of Lactobacillus johnsonnii NCC by supplementing growth medium with unsaturated fatty acids. Anhydrobiotics: the challenges of drying probiotic cultures. Food Chemistry. Proteins and temperature. Annu Rev Physiol. Identification of sites of injury in Lactobacillus bulgaricus during heat stress.
J Appl Microbiol. Alternative drying processes for the industrial preservation of lactic acid starter cultures. Biotechnol Prog. Lyophilisation - introduction and basic principles. Weinheim: Wiley-VCH; Viability of lactic acid bacteria and bifidobacteria in fermented soymilk after drying, subsequent rehydration and storage. Int J Food Microbiol. Stress responses in lactic acid bacteria. Antonie Van Leeuwenhoek; Cold shock and its effect on ribosomes and thermal tolerance in Listeria monocytogenes.
Cold shock response in Bacillus subtilis. J Mol Microbiol Biotechnol. Oxidative stress in Lactococcus lactis. Genet Mol Res. Roles of thioredoxin reductase during the aerobic life of Lactococcus lactis. J Bacteriol. Genomic insights into bifidobacteria. Microbiol Mol Biol Rev. Progress in genomics, metabolism and biotechnology of bifidobacteria. Bifidobacterium psychraerophilum sp. Int J Syst Evol Microbiol. Sensitivity of bifidobacteria to oxygen and redox potential in non-fermented pasteurised milk.
Improved viability of bifidobacteria in fermented milk by cocultivation with Lactococcus lactis subspecies lactis. J Dairy Sci. Identification of Lactobacillus sakei genes induced during meat fermentation and their role in survival and growth. Global transcriptional response of Lactobacillus reuteri to the sourdough environment.
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Effect of time of inoculation, starter addition, oxygen level and salting on the viability of probiotic cultures during Cheddar cheese manufacture. In vitro tolerance to digestive stresses of propionibacteria: influence of food matrices. Food Microbiol. Life under stress: the probiotic stress response and how it may be manipulated.
Curr Pharm Des. The interaction between bacteria and bile. Susceptibility and adaptive response to bile salts in Propionibacterium freudenreichii : physiological and proteomic analysis. Environmental stress responses in Lactobacillus : a review. Molecular chaperones in lactic acid bacteria: physiological consequences and biochemical properties. J Biosci Bioeng. Curr Opin Biotechnol. Lactobacillus acidophilus nucleic acid sequences encoding stress-related proteins and uses thereof. Patent No. Environmental adaptation of probiotic lactobacilli towards improvement of performance during spray drying.
Small heat shock proteins are molecular chaperones. J Biol Chem. Alpha-crystallin-type heat shock proteins: socializing minichaperones in the context of a multichaperone network. The small heat-shock protein IbpB from Escherichia coli stabilizes stress-denatured proteins for subsequent refolding by a multichaperone network.
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Cloning, molecular characterization and expression analysis of two small heat shock genes isolated from wine Lactobacillus plantarum. Cloning and characterization of the hsp Res Microbiol. Inactivation of a small heat shock protein affects cell morphology and membrane fluidity in Lactobacillus plantarum WCFS1.
Improved adaptation to heat, cold, and solvent tolerance in Lactobacillus plantarum.
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Appl Microbiol Biotechnol. Improved adaptation to cold-shock, stationary-phase, and freezing stresses in Lactobacillus plantarum overproducing cold-shock proteins.
Patho-biotechnology: using bad bugs to do good things. Bacterial osmoadaptation: the role of osmolytes in bacterial stress and virulence. Osmoadaptation in bacteria. Adv Microb Physiol. Microbial water stress. Bacteriol Rev. Enzyme stabilisation by ectoine-type compatible solutes: protection against heating, freezing and drying. Ecological significance of compatible solute accumulation by micro-organisms: from single cells to global climate. Heterologous expression of BetL, a betaine uptake system, enhances the stress tolerance of Lactobacillus salivarius UCC Betaine and carnitine uptake systems in Listeria monocytogenes affect growth and survival in foods and during infection.
Identification and disruption of BetL, a secondary glycine betaine transport system linked to the salt tolerance of Listeria monocytogenes LO A postgenomic appraisal of osmotolerance in Listeria monocytogenes. Role for compatible solutes glycine betaine and L-carnitine in listerial barotolerance.
Improving gastric transit, gastrointestinal persistence and therapeutic efficacy of the probiotic strain Bifidobacterium breve UCC Biliary excretion as possible origin of Listeria monocytogenes in fecal carriers. Am J Vet Res. Extracellular replication of Listeria monocytogenes in the murine gall bladder. Mol Microbiol. Enhancing bile tolerance improves survival and persistence of Bifidobacterium and Lactococcus in the murine gastrointestinal tract. BMC Microbiol. Contribution of three bile-associated loci, bsh , pva , and btlB , to gastrointestinal persistence and bile tolerance of Listeria monocytogenes.
Infect Immun. Relationship between the resistance to bile salts and low pH with exopolysaccharide EPS production of Bifidobacterium spp. Association of beta-glucan endogenous production with increased stress tolerance of intestinal lactobacilli. Water-soluble dietary fibers and cardiovascular disease. Physiol Behav. Reduced and high molecular weight barley beta-glucans decrease plasma total and non-HDL-cholesterol in hypercholesterolemic Syrian golden hamsters.
J Nutr. Effects of beta-glucans on the immune system. Medicina Kaunas ; 43 — Dietary modulation of immune function by beta-glucans. Mutat Res. Supplementation of the diet with high-viscosity beta-glucan results in enrichment for lactobacilli in the rat cecum.
Expression of a heterologous manganese superoxide dismutase gene in intestinal lactobacilli provides protection against hydrogen peroxide toxicity. Marker-free chromosomal integration of the manganese superoxide dismutase gene sodA from Streptococcus thermophilus into Lactobacillus gasseri. Expression of the catalase gene katA in starter culture Lactobacillus plantarum TISTR tolerates oxidative stress and reduces lipid oxidation in fermented meat product. High-level expression of heme-dependent catalase gene katA from Lactobacillus sakei protects Lactobacillus rhamnosus from oxidative stress.
Mol Biotechnol. Coexpression of bile salt hydrolase gene and catalase gene remarkably improves oxidative stress and bile salt resistance in Lactobacillus casei. J Ind Microbiol Biotechnol. Trained and licensed mental health professionals can provide support in helping you to find relief from your symptoms. Psychotherapy can help individuals identify what issues are contributing to their symptoms of depression and how best to address these issues.
As the American Psychological Association reports, psychotherapy can help reduce symptoms of depression and also prevent future episodes of depression. Additionally, research has shown that the relationship between the therapist and client is central to positive change in therapy. If you have been to therapy before and didn't find it helpful, don't assume that it can't ever be helpful; it may be that the therapist was not a good fit for you.
Many college campuses provide on campus counseling centers for students to access at little to no cost. Therapists on college campuses will often have been hired for their ability to connect with and support college students. There are many reasons to access counseling services through your school. The National Alliance on Mental Illness NAMI conducted a survey report on college students and mental health and found that one critical benefit of college counseling centers is that staff are able to coordinate with the school's Disability Resource Center DRC if a student requires accommodations.
If your depression, or any other mental health challenge is impacting your ability to engage in your studies successfully you can request special accommodations. We encourage you to begin your search for a therapist with your campus counseling center. Information about how to access your campuses counseling center should be available on your college or university's website.
If you would prefer to meet with a therapist or counselor off campus for any reason a good place to start your search is with the find a therapist tool run by Psychology Today. If you are experiencing symptoms of depression it is generally a good idea to talk with your primary care provider about this. Your doctor can help you rule out or treat any medical issues that may be contributing to symptoms of depression. Nurse practitioners, doctors, and psychiatrists can all prescribe medication to treat depression.
After talking with you about your specific symptoms your medical provider may request that you try meeting with a mental health therapist before starting medication. However, sometimes psychotherapy is not enough for more severe forms of depression and you, your therapist, and your doctor may decide that medication would be helpful.
Fortunately, advances in medicine have provided a number of medications that can be effective in treating depression. The Mayo Clinic outlines several common medications for treating depression. Mindfulness can be defined as staying aware and conscious in the present moment. While it sounds simple, being mindful is not easy, it can take a great deal of practice to develop the ability to be conscious and connected in the present moment.
College students may find themselves managing so many different commitments classes, work, friends at a time that they have a hard time staying focused without thinking about what they need to do next. And it can seem almost impossible to imagine staying in the present moment when managing frequent distractions on our ever present phones.
However, there is hope because there are many ways to go about learning about and practicing mindfulness exercises such as: meeting with a therapist who emphasizes mindfulness; going to a yoga class -some classes emphasize mindfulness more than others; reading about different mindfulness exercises and practicing them on your own; listening to audio mindfulness meditations; and attending a meditation class or retreat. As NPR reports, meditation is a mindfulness practice that has been shown to help people manage depression.
There is a model of therapy called Mindfulness-Based Cognitive Therapy that an individual can engage in through working with a therapist but there are also countless mindfulness exercises that people can practice on their own at home. The American Psychological Association APA reports that mindfulness-based therapies can be helpful in not only treating depression but also in reducing relapse rates among individuals diagnosed with depression.
Another benefit of most mindfulness exercises is that you can practice them anywhere, anytime without anyone knowing, even in class or a crowded student union. So if you find yourself in a stressful situation or notice yourself experiencing one of the may cognitive symptoms of depression, something as quick and simple as a breathing exercise may be just what you need to get you back on track and through your day.
It may seem simplistic but spending time in nature has been shown to reduce symptoms of depression. There is a model of therapy built around the philosophy that spending time in, and connecting with, nature will improve mental health. This is called ecotherapy , and is also known as green therapy, or nature therapy.
There is lots of research to back up ecotherapy. The benefits of spending time outdoors in nature have been looked at by researchers all over the world. In Japan there is a custom called forest bathing, which essentially means spending time around trees. As Quartz reports, "The Japanese practice of forest bathing is proven to lower heart rate and blood pressure, reduce stress hormone production, boost the immune system, and improve overall feelings of well being.
Even a 30 minute walk in a green setting has been shown to have an impact. Many college campuses are located in beautiful settings with easy access to walking or hiking trails. Finding time to sneak away even once a week could have a significant impact on your mental health. And if you are in school in a big city where you don't get much connection to nature, it may be even more important for you to find time to make a trip to the country, the coast, or the mountains every once in awhile just to get a dose of what nature has to offer.
An added benefit of spending time in nature is that usually while in nature people are doing some form of exercise, such as walking, hiking, running, skiing, or swimming which also helps reduce depression. Exercise has countless physical health benefits such as strengthening your heart, lowering blood pressure, reducing body fat, and improving strength. Exercise has also been shown to have numerous mental health benefits including reducing stress, anxiety, and depression. College students can also benefit from the impact that exercise has on the brain including improved memory and thinking skills.
As WebMD explains, research has proven the benefits of exercise for treating mild to moderate depression but it is often under utilized. It may be hard as a college student experiencing depression to imagine finding the motivation or time to exercise. The good news is that colleges and universities often invest in recreational resources for students. Most colleges and universities offer campus recreation centers with gyms stocked with stationary bikes and treadmills as well as weight rooms, basketball courts, and swimming pools.
Most colleges and universities also offer exercise classes and intramural sports that you can join. Your student fees are paying for these resources whether you use them or not, so why not check it out! If getting to the gym feels like too much to start with, simply walking to class rather than taking the bus or driving could give you the emotional boost you need.
Active reports that walking for 30 minutes three to four times a week can improve your mood, and that even "if a 20 minute power walk at lunchtime is all you manage, after six weeks it could be comparable to a course of psychotherapy". When you exercise you produce endorphins which leads to increased feelings of well being.
So it doesn't matter what you do as long as you get your heart rate up. Exercise can be anything that you enjoy doing, so if you don't feel like hitting the gym or going for a run then call a friend and go for a walk or get a group of friends together for a round of disc golf or another group sport.
Connecting with friends while walking or playing a game will take your mind off the exercise, and will give you the added benefit of social support. Going to college often means moving away from friends and family and starting a new life in a new town or city and meeting all new people. This can be hard and overwhelming at first. Putting time and energy into meeting new people and developing friendships is important for your mental health. The International Journal of Mental Health Systems found that social support minimized the effects of stress on depression for college students.
Because stress can exacerbate symptoms of depression it is important to know that social connection can reduce the impact of stress. If you are feeling depressed it is likely that you may not be engaging in all the activities you once were.