University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Surface structures involved in plant stomata and leaf colonization by shiga-toxigenic Escherichia coli o157:h7

Abstract: Shiga-toxigenic Escherichia coli (STEC) O157:H7 uses a myriad of surface adhesive appendages including pili, flagella, and the type 3 secretion system (T3SS) to adhere to and inflict damage to the human gut mucosa. Consumption of contaminated ground beef, milk, juices, water or leafy greens has been associated with outbreaks of diarrheal disease in humans due to STEC. The aim of this study was to investigate which of the known STEC O157:H7 adherence factors mediate colonization of baby spinach leaves and where the bacteria reside within tainted leaves. We found that STEC O157:H7 colonizes baby spinach leaves through the coordinated production of curli, the E. coli common pilus (ECP), hemorrhagic coli type 4 pilus (HCP), flagella, and T3SS. Electron microscopy analysis of tainted leaves revealed STEC bacteria in the internal cavity of the stomata, in intercellular spaces, and within vascular tissue (xylem and phloem), where the bacteria were protected from the bactericidal effect of gentamicin, sodium hypochlorite or ozonated water treatments. We confirmed that the T3S escN mutant showed a reduced number of bacteria within the stomata suggesting that T3S is required for the successful colonization of leaves. In agreement, non-pathogenic E. coli K-12 strain DH5α transformed with a plasmid carrying the LEE pathogenicity island, harboring the T3SS and effector genes, internalized into stomata more efficiently than without the LEE. This study highlights a role for pili, flagella, and T3SS in the interaction of STEC with spinach leaves. Colonization of plant stomata and internal tissues may constitute a strategy by which STEC survives in a nutrient-rich microenvironment protected from external foes and may be a potential source for human infection.

Grade Changes in Brain–Body Allometry: Morphological and Behavioural Correlates of Brain Size in Miniature Spiders, Insects and Other Invertebrates

Abstract: We use a recent wave of data to confirm that Haller's rule of brain–body allometry, for smaller species to have relatively larger brains, holds for invertebrates as well as vertebrates But different invertebrate taxa fall on several different allometric lines (grades) In the smallest animals in several grades, the brain occupies a large fraction (up to approximately 16%) of the total body mass The brain and the structures enclosing it show morphological alterations suggesting a lack of housing capacity in the head for the brain (eg the brain extends into other parts of the body such as the legs or thorax), and other structures normally enclosed in the same area are displaced Miniature animals may thus sacrifice some morphological aspects of body design to accommodate their disproportionately large CNS The smallest animals of one such group, orb web spiders, do not show signs of behavioural limitation in web construction compared with larger relatives We speculate that, because of selection resulting from the high metabolic costs of nervous tissue, grade changes may involve substantial modifications of how brains function, and help explain differences between neuron-profligate vertebrates and invertebrates having far fewer neurons (as few as approximately 200–500 neurons in two groups) Scaling problems associated with small size are of general importance, because many moderate-sized animals have very small free-living immature stages