Search

Plants associate with communities of microbes (bacteria and fungi) that play critical roles in plant development, nutrient acquisition and oxidative stress tolerance. The major share of plant microbiota is endophytes which inhabit plant tissues and help them in various capacities. In this article, we have reviewed what is presently known with regard to how endophytic microbes interact with plants to modulate root development, branching, root hair formation and their implications in overall plant development. Endophytic microbes link the interactions of plants, rhizospheric microbes and soil to promote nutrient solubilization and further vectoring these nutrients to the plant roots making the soil-plant-microbe continuum. Further, plant roots internalize microbes and oxidatively extract nutrients from microbes in the rhizophagy cycle. The oxidative interactions between endophytes and plants result in the acquisition of nutrients by plants and are also instrumental in oxidative stress tolerance of plants. It is evident that plants actively cultivate microbes internally, on surfaces and in soils to acquire nutrients, modulate development and improve health. Understanding this continuum could be of greater significance in connecting endophytes with the hidden half of the plant that can also be harnessed in applied terms to enhance nutrient acquisition through the development of favourable root system architecture for sustainable production under stress conditions.

Aims: In previous studies the microbial kinetics of Escherichia coli K12 have been evaluated under static and dynamic conditions (Valdramidis et al. 2005, 2006). An acquired microbial thermotolerance following heating rates lower than 0·82°C min−1 for the studied micro-organism was observed. Quantification of this induced physiological phenomenon and incorporation, as a model building block, in a general microbial inactivation model is the main outcome of this work. Methods and Results: The microbial inactivation rate observed (kobs) under time-varying temperature conditions is studied and expressed as a function of the heating rate (dT/ dt). Hereto, a model building block related to the microbial physiology (kphys) under stress conditions is developed. Evaluation of the performance of the developed mathematical approach depicts that physiological adaptation is an essential issue to be considered when modelling microbial inactivation. Conclusions: Consideration, at a mathematical level, of microbial responses resulting in physiological adaptations contribute to the reliable quantification of the safety risks during food processing. Significance and Impact of the Study: By taking into account the physiological adaptation, the microbiological evolution during heat processing can be accurately assessed, and overly conservative or fail dangerous food processing designs can be avoided.

Aims: To study the survival processes of thermophilic Campylobacter spp. within a modelled aquatic system and particularly the involvement and survival potential of viable but non-culturable forms. Methods and Results: The survival and morphological characteristics of populations of thermophilic Campylobacter species exposed to simulated aquatic conditions were examined using a combination of cultural and microscopic techniques. Populations underwent progressive decay when exposed to simulated aquatic conditions. The rates of population decay were observed to be significantly greater at the higher temperature (20°C) with a rapid transition of the dominant sub-populations from non-stressed to dead cells occurred within 3 days. At 10°C the rate of culturability loss was much reduced with substantial development (approx. 80% of total population) of viable but non-culturable (VBNC) populations by all species within 3 days, declining to represent approximately 5–25% of the total population at day 60. Significant differences (P

Studies describing the survival of Escherichia coli in foods, more often than not use the O157:H7 serovar as the target organism. Whilst E. coli O157:H7 is undoubtedly the predominant agent of concern for foodborne disease caused by enterohaemorrhagic E. coli (EHEC), a consequence of this concern is the commonly held view that this one serovar is 'atypical' in its response to stress conditions and therefore better able to survive adverse environments. Many of the studies published do not make comparisons with other E. coli (either commensal organisms or other pathogenic types) or other members of the Enterobacteriaceae, that would justify this view. Nevertheless, there has been a great deal of valuable data and information generated describing the fate of E. coli O157:H7 in a range of foods stored under various conditions. In many respects, the results of these studies are not surprising considering the survivability of other closely related pathogens, such as Shigella spp. This ability to survive in foods for long periods of time confirms the need for reliable control measures where contamination is possible or likely, e.g. proper handling and thorough cooking of beefburgers. The factors that may influence survival in different foods are described, with the intention of providing an insight in this area of food safety. Key considerations for carrying out survival studies are identified, with particular reference to methodologies used.