During germination phase I, cation and DPA dipicolinic acid release, partial core hydration and SASP degradation occur, with cortex hydrolysis and further core hydration during germination phase II, followed by biosynthetic processes, escape from spore coats and eventual cell division. During periods of stress, trophozoites of Acanthamoeba spp. Extensive changes occur during encystation in A. Resistance to several biocides commences with the synthesis of the cellulose-containing wall, implying that a physical barrier is responsible for this decreased susceptibility rather than it being a consequence of a metabolically dormant cyst.
The rates of propidium iodide penetration were substantially higher in filamentous forms when exposed to CHX. Applied stress is i any deviation from the optimum growth condition that produces a reduced growth rate, ii exposure to an environmental situation that produces damage to cellular components in the absence of a cellular response, or iii a situation that stimulates the expression of genes known to respond to a specific environmental condition.
Stress adaptation refers to the ability of bacteria or other microorganisms to adapt to a chemical or other applied stress. Gould pointed out that vegetative bacterial cells react homeostatically to stress in a variety of ways; these include the activation and expres-sion of latent groups of genes following exposure to oxidative stress.
Oxidative stress and the SOS response in E. When E. This is essential for long-term survival of the cell and is partly mediated by alternative sigma factors.
Programmed cell death PCD is a programmed suicide mechanism, with persisters being defective in PCD and using the exudate from lysed cells as a source of nutrient. Highly metabolic cells, which are more susceptible to biocides, can be readily differentiated from stationary phase cells by this phenomenon. The adaptational network of B. Stress response proteins are induced when sporulating cells are heat-shocked. Stress adaptation responses are also known in yeasts. These responses are i intrinsic constitutive and depend on growth phase and the stage of an organism in its life cycle, or ii inducible.
These can damage cellular nucleic acids, proteins and lipids. The main defence systems in S. As with vegetative bacterial cells, yeast cells can adapt to a subsequent dose of hydrogen peroxide.
During this adaptation, several polypeptides are induced, some of which are unique to peroxide treatment with others also being produced following heat shock. Catalase and possibly glutathione play a role in this adaptive response. Stresses such as heat, oxidative stress and pH shock on Acanthamoeba trophozoites have been studied. Resistance to biocidal agents has been widely studied in bacteria 11 and to some extent in fungi, 27 with some useful information beginning to emerge with some types of protozoa Table 5.
Gram-negative bacteria, and especially P. This aspect has been considered in greater detail elsewhere. This could prove to be a worthwhile investigation. In terms of their biocide susceptibility, mycobacteria occupy an intermediate position between bacterial spores and other bacteria.
The major reason for their recalcitrance to biocide activity is the lipid-rich, waxy cell wall which limits intracellular uptake of many biocides. Bacterial spores tend to be much less susceptible to biocidal agents than non-sporulating bacteria.
An obvious reason is to be found with the nature and composition of the spore coats and possibly cortex Table 1 which present an effective permeability barrier to the entry of many biocides. Antibiotic resistance in yeasts is known to occur via target site mutations and reduced uptake impermeability and efflux. However, when used in combination with the polyenic antifungal drug, amphotericin B which combines with fungal membrane sterol , it shows activity against several fungal species.
This has led to the suggestion that increased uptake of rifampicin occurs as a consequence of amphotericin action and that membrane sterols pose a barrier to its entry. CHX and QACs cause damage to the yeast plasma membrane; , 51 , 52 it is not, however, known whether this interaction is reduced by the presence of membrane sterols which could effectively limit further uptake into the cell interior.
The outer layers of protozoal cysts are likely to act as a barrier to some biocides. The outer shell of Cryptosporidium oocysts renders them more resistant to biocides. Biocides are considered to be multitargeted chemical agents. Mutation in the target enzyme or its overproduction can lead to considerable increases in MICs.
With alcohols, the lipid composition and plasma fluidity play a role in the susceptibility of yeasts. Efflux is a major mechanism for the resistance shown by bacteria to antibiotics. Efflux of antifungal antibiotics has also been described. The mechanisms of reduced susceptibility to biocides and antibiotics of bacterial cells present within biofilms have been the subject of considerable experimentation and debate.
In nature, it is likely that biofilms will consist of mixed populations of different types of microorganisms. Many types of bacteria and yeasts interact with protozoa, e. Legionella pneumophila within Acanthamoeba cysts are protected from the action of chlorine.
With algae, the presence of mats equates to biofilms and constant dosing with biocides may be needed to prevent algal recontamination. These can coat spore DNA, thereby protecting it from damage by enzymes and antibacterial agents.
They thus play an important role in determining spore susceptibility to antibacterial agents. It is important to understand the reactions of different types of microorganisms to biocidal agents.
This is useful from the point of view of cell structure and physiology but also provides valuable information about i the mechanisms of action of biocides, ii the mechanisms whereby microorganisms resist biocide action, and iii the improved usage of biocides in clinical and environmental situations.
With the emergence of new pathogenic organisms and the current level of concern about microbes used as bioterrorism weapons, it is increasingly important to understand the actions and effects of biocidal agents on as wide a range of organisms as possible and of how organisms might resist those actions.
Additionally, yeasts and fungi are more closely related to mammalian cells than originally thought and can be used as screening tools to elucidate the mechanisms of action of antineoplastic agents.
It is clear that antibiotics generally are very selective for the type of organism against which they are used. This implies that different organisms, despite their varied structures, have similar target sites, although with algae, for example, so many different types are known that it is impossible to generalize. In particular, when considering the mechanisms of antimicrobial activity of biocidal agents, compounds that interact with proteins, enzymes or nucleic acids are likely to be effective against a wide range of microorganisms probably as a result of the same basic actions.
The reasons for the variations in non- susceptibility arising between different types of microorganisms can then be ascribed to: i the considerable differences in adsorption by and uptake into cells resulting from the dissimilarities in chemical composition and architecture of the outer cell layers—this is an area where much additional information is needed, but is clearly of considerable importance. Concentration is a key issue in biocide activity 1 and is particularly relevant to the present discussion; ii possible slight or marked differences in the actual target site s so that the affinity of the site s for a biocide is modified; iii possible differences in the amounts of available target site s ; iv the presence within some types of cells of protective chemicals such as the spore-specific SASPs that protect against DNA damage; v stress responses, i.
For example, an SOS response, an efflux pump safety mechanism, or biocide degradation actually unlikely at in-use concentrations of biocide, although one claimed mechanism for the reduced susceptibility of biofilm cells in different types of microbial cells must be considered; and vi the presence of a biofilm an increasingly important field of study or, in the case of algae, a mat, that is responsible for the recalcitrance shown by cultures to biocides.
Further investigations on the relative responses of different types of microbes to biocides should build on current knowledge with the ultimate overall aim of achieving greater understanding of the action and resistance mechanisms involved and of the control of microbial inactivation processes. Figure 1. Relative susceptibility of entities prions, viruses and microorganisms to biocides. Algae not shown, but likely to be susceptible to at least some biocides.
Figure 2. General pattern of biocide entry into different types of microorganisms for simplicity, no barrier function is envisaged. Figure 3. Sporogenesis and susceptibility and resistance to biocides. For role of SASPs, see text. The yeast S. McDonnell, G. Antiseptics and disinfectants: activity, action and resistance.
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Bees from hives placed in the desert have been observed to fly as far as Thus, the honey bee system shows potential for applications such as detecting the presence and location of environmental indicator microorganisms and plant pathogens.
In the latter case, bees pollinating crop plants may pick up pathogens from the plants themselves, as well as from the air around them, increasing their effectiveness as a collection and detection tool. Finally, the honey bee system may have potential as an early detector of biological warfare or bioterrorism agents before the appearance of disease symptoms.
We will also investigate the lower limits of aerosol concentrations that are detectable with this method. We thank A. Mohr U. Colin M. E Richard D Chauzy S. Measurement of electric charges carried by bees: evidence of biological variations. Google Scholar. Corbet S. A Beament J Eisikowitch D. Are electrostatic forces involved in pollen transfer?
Plant Cell Environ. Eckert J. The flight range of the honeybee. Erikson E. Surface electric potentials on worker honeybees leaving and entering the hive. Gary N. E Witherell P. C Marston J. Foraging range and distribution of honey bees used for carrot and onion pollination. Ghisalberti E. Propolis: a review. Bee Worl. Grange J. M Davey R. Antibacterial properties of propolis bee glue. Bees scavenge airborne bacteria.
Mason B. The physics of clouds. Oxford , Clarendon , Google Preview. Pasquill F Smith F. Atmospheric diffusion. Chichester , England , Ellis Horwood , Peterson E. W Lighthart B. Estimation of downwind viable airborne microbes from a wet cooling tower-including settling. Yes'kov Y. K Sapozhnikov A. Mechanisms of generation and perception of electric fields by honey bees. Biofizika , 21 : — Oxford University Press is a department of the University of Oxford.
Given the importance of the killing of spores of Bacillus species in the food and medical products industry, a deeper understanding of the mechanisms of spore resistance and killing may lead to improved methods for spore destruction.
Abstract A number of mechanisms are responsible for the resistance of spores of Bacillus species to heat, radiation and chemicals and for spore killing by these agents. Publication types Research Support, N. Further, Bacillus strains also possess biotherapeutic potential which is connected with their ability to interact with the internal milieu of the host by producing variety of antimicrobial peptides and small extracellular effector molecules.
Nonetheless, with proposed scientific evidences, commercial probiotic supplements, and functional foods comprising of Bacillus spp. This review highlights the probiotic candidature of spore forming Bacillus spp. Moreover, the growing need to evaluate the safety of individual Bacillus strains as well as species on a case by case basis and necessity of more profound analysis for the selection and identification of Bacillus probiotic candidates are also taken into consideration.
The interest in the field of beneficial microbes has emerged multiple folds since its inception by the Russian Noble laureate, Elie Metchnikoff. The term Probiotics, taken as an un-challenged synonym to beneficial microbes, has gained popularity over the years and has found application in several general health and clinical scenarios. Probiotic formulations are being developed and standardized for both human and animal consumption.
Probiotics have also found application in animal feed for prevention of gastrointestinal infections, with extensive use in the poultry and aquaculture industries Hong et al. The consumer awareness, search for alternate, safe and cost-effective treatments, and concern of developing antibiotic resistance has compelled researchers to find an alternate to ongoing therapeutic regimes, mainly dependent over antibiotics.
Among the large number of suggested options, probiotic therapy seems to be the most viable one, with long history of consumption and assured safety. LAB and Bifidobacterium spp. Other preferred bacteria include strains of Enterococcus, Streptococcus and Bacillus spp. Majeed et al. Several reference probiotic strains have been shown to play a potential role in management of several clinical scenarios viz.
Mallappa et al. It has been clearly understood that the gut inhabitants and their proper balance is the foremost criteria that determines healthy status, particularly in terms of metabolic disorders Wang et al. Research updates from several in vivo Ellekilde et al. Besides the commonly explored strains, bacterial spore formers, mostly of the genus Bacillus do carry probiotic attributes. The value of non-spore former LAB for the maintenance of human and animal health has been acknowledged both scientifically in terms of published research data and commercially in form of the availability of probiotic products.
However, in comparison to LAB, bacterial spore formers have not gained high popularity, particularly in terms of research interest Figure 1. Several Bacillus strains have been screened for their potential probiotic functionalities, in several in vitro and in vivo models.
Besides qualifying the mandatory bench marks for a candidate probiotic; Bacillus spp. Additionally, they have also been shown to possess pathogen exclusion, anti-oxidant, antimicrobial, immuno-modulatory Lefevre et al.
Furthermore, scientific reports supported with evidence of safe use and long history of consumption supports the candidature of spore formers as potential probiotics and as functional food supplements due to their significant capacity of production of extracellular enzymes.
Bacillus spp. Different species of Bacillus has also been used for the production of additional nutraceuticals including vitamins e. Nevertheless, despite above benefits, these strains have not gained much importance and attention in current functional food industry due to their relatedness with few human pathogens.
Few of the members of Bacillus spp. Among them, Cereulide produced by B. Thereby, to understand the nature of beneficial spore former probiotic strains, their probiotic potential and safety concerns are important; not only because of their complexity and behavior in human GIT, but also due to their allochthonous free living nature, questioning their ability to colonize in the human gut Hong et al. Though, the members of Bacillus genus have been consumed in the form of fermented foods since long time Tamang et al.
The associated safety and licensing issues that influence the use of Bacillus spp. Bacillus signifies a Gram-positive, rod shaped, spore-forming, aerobic or facultative anaerobic bacterium.
In general, the genus Bacillus is designated as a group of soil inhabitants. However, Bacillus spp. Nevertheless, Bacillus spp. Some distinct species have also been recognized as opportunistic pathogen or toxin producer in human or animal hosts. The genus Bacillus is closely related to Lactobacillus spp.
Both share the same class, Bacilli under the phylum Firmicutes Figure 2. Looking toward the probiotic prospective, it is proclaimed that the candidate probiotic should be isolated from the gut of the target population, which helps them to thrive well within the gut. However, elementary attributes of native flora for survivability are not essential for spore-former s.
Bacillus spores can survive in extreme acidity of stomach, and tolerate bile salts and other hostile conditions of GIT. Besides, bacilli are more stable during processing and storage of food and pharmaceutical preparations, which make them more suitable ingredient for health promoting formulations. Thereby, in addition to human sources, Bacillus strains with probiotic attributes are also isolated from fermented or unfermented food sources Adewumi et al.
TABLE 1. Examples of probiotic supplements containing Bacillus spp. It is believed that Bacillus spp. They get colonized in to the intestinal tract after consumption of vegetables or raw food materials contaminated with soil microflora. Moreover, ingestion of fermented cereals or beans, such as Iru and Natto also make their way in to the intestine. Findings from in vitro studies claim that vegetative cells and spores of B.
However commensal gut microbiota possesses inhibitory activity against them Berthold-Pluta et al. A study by Tam et al. The 16S rRNA gene phylogenetic analysis of isolates demonstrated the presence of 10 different Bacillus species in examined fecal samples of 30 volunteers Tam et al. Hoyles et al. Two species, B. To find out the stage of Bacillus in human gut, Casula and Cutting targeted a genetically engineered chimeric gene, ftsH-lacZ , which is selectively and strongly expressed in the vegetative cells of Bacillus subtilis and reported their presence throughout the GIT.
They stated that the spores germinated in significant numbers in the jejunum and ileum, suggesting their colonization into the small intestine. Recently, Ghelardi et al. Nevertheless, the impact of allochthonous Bacillus strains on the profile of fecal flora of the host during transition period has been proven significant. Nyangale et al.
Likewise, a study by Adami and Cavazzoni in piglet model has also shown that the feeding of Bacillus coagulans CNCM I increased aerobic and anaerobic sporeformers, decreased lactococci, enterococci, anaerobic cocci, and fecal coliforms in the treatment group. The consumption of vegetative cells and spores of Bacillus spp.
A diverse range of Bacillus species are found to be associated to the natural fermentation of soy, locust been, maize, rice and many more substrates. These fermented products exhibit unique sensory attributes, probably due to the activity of extracellular carbohydrate and protein degrading enzymes of Bacillus spp. The palatability and health promoting characteristic of these locally produced supplements has also attracted the attention of global market.
A diverse range of LAB and Bacillus spp. Respectively, the strains of B. Bacillus strains are also getting recognition as potential probiotics which could promote human health by direct consumption of high concentrations of viable number of cells Abdhul et al.
Several Bacillus probiotic strains have been approved by regulatory agencies of different countries for human use and are popular as general health promoting pharmaceutical formulations in global market Table 1. So far commercial products of Bacillus composing functional foods are not popular in nutraceuticals market because the debate over probiotic vs. The genus Bacillus has undergone considerable taxonomic changes over time.
With the advent of molecular taxonomy, Ash et al. In this review, we are looking over the significance and approach of Bacillus probiotics in current scenario.
According to Ash et al. Evolutionary distance tree showed specific relation between species, for example, there were three distinct clades of closely related species. First clade included B. Second and third clades comprised of B. However, all remaining members of the group did not show any significant relationship with them. Group 2, 3, 4, and 5 consisted of 7, 10, 2, and 3 species respectively. Interestingly, the available data points out that both the probiotic Bacillus species e.
Therefore, more deep analysis of the taxonomic positions of these species is needed to reach a definite conclusion. In this study, comparative sequence analysis of the 16SS ITS sequences, revealed 10 distinct phylogenetic clusters. Twenty-six evaluated Bacillus species were separated in seven groups; with groups II, V, VI, and X comprising of seven, two, nine and five Bacillus species, respectively Figure 3.
Bacillus subtilis , the type species fall in Group VI along with B. This study revealed that two major pathogenic spp. Interestingly, B. The pathogenic characteristic depends over strain and variety specific production of several extracellular factors viz. Toxicity of virulent forms of B. Recently, data obtained from draft genome assemblies of 25 B.
Frequent horizontal transfer of pathogenicity factors among B. The enterotoxin operons viz. Phylogenetic relationships of 46 Bacillus species. The bar represents the unit length of the number of nucleotide substitutions per site adopted from Xu and Cote, These studies have revealed the phylogenetic relations among important species of Bacillus genus and are also indicating toward the necessity of more profound process for the selection and identification of Bacillus probiotic candidates.
In this way, the complete genome sequencing and comparative analysis of various close relative Bacillus species of different groups has been provided by different research groups Rey et al. The data of deeply sequenced Bacillus species from different sources can be utilized for the accurate identification and characterization of candidate probiotic strains. In order to qualify as a potential probiotic candidate, the Bacillus strains must possess the primary requirement of GIT stress tolerance, besides having good adhesion and bio-therapeutic properties Thakur et al.
Survival under the GIT stress represents another challenge for safe transit and localization in the gut. Bacilli are normally considered soil organisms however, number of them including B.
In this regard, Hong et al. Earlier, Hyronimus et al. Also, B. This study indicated high acid tolerance of Bacillus spp. Similar to non-spore forming Lactobacillus spp. Additionally, food matrix also plays an important role in survival of probiotics during simulated gastric juice conditions Karu and Sumeri, Different Bacillus strains have been reported to display antimicrobial, anti-oxidative and immune-modulatory activity in the host.
The elements behind beneficial attributes of Bacillus spp. The antagonistic activity of Bacillus spp. A study by Pinchuk et al. The antagonistic activity of aninocoumacin A was also documented against enteric E. An interesting communication by Ripert et al. This activity was mediated by serine protease s of B. On the other hand, exclusion of pathogen by the inhibition of bacterial biofilm is another potential attribute proposed for Bacillus strains.
In this context, Gobi et al. Recently, a bacteriocin producing strain of probiotic Bacillus coagulans had been isolated from traditional fermented fish of Manipur, India. The purified bacteriocin of low molecular weight displayed broad spectrum of antimicrobial activity against food borne and related clinically relevant pathogens, besides having lower cytotoxicity Abdhul et al.
Earlier, Joseph et al. Such bacteriocin producing strains of Bacillus spp. In spite of pathogenic status of B. For example, B. However, it was also found to produce enterotoxins Duc et al.
In addition, B. In the food sector, the global trend is to incorporate probiotics into food matrix in order to provide some health-promoting component s beyond its traditional nutrients Butel, Lactobacillus and Bifidobacterium spp. On contrary, there are few published reports dealing with the health benefits of probiotic spore formers Figure 1.
Efficacy of Bacillus spp. The available data from these studies has presented the beneficial effects of different strains of Bacillus spp. For example, several researchers have recognized the preventive role of Bacillus probiotic in gut physiology impairment conditions Lopetuso et al.
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