Synthetic Scaffold Systems for Increasing the Efficiency of Metabolic Pathways in Microorganisms

Microbes have been the preferred hosts for producing high-value chemicals from cheap raw materials. However, metabolic flux imbalance, the presence of competing pathways, and toxic intermediates often lead to low production efficiency. The spatial organization of the substrates, intermediates, and enzymes is critical to ensuring efficient metabolic activity by microorganisms. One of the most common approaches for bringing the key components of biosynthetic pathways together is through molecular scaffolds, which involves the clustering of pathway enzymes on engineered molecules via different interacting mechanisms. In particular, synthetic scaffold systems have been applied to improve the efficiency of various heterologous and synthetic pathways in Escherichia coli and Saccharomyces cerevisiae, with varying degrees of success. Herein, we review the recent developments and applications of protein-based and nucleic acid-based scaffold systems and discuss current challenges and future directions in the use of such approaches.

Variable host responses mediate host preference in marine flatworm−snail symbioses

Host preference of symbionts evolves from fitness trade-offs. However, it is often unclear how interspecific variations in host response traits influence this evolutionary process. Using the association between the polyclad flatworm Paraprostatum echinolittorinae and its intertidal snail hosts on the Pacific Coast of Panama, we assessed how a symbiont’s host preference is associated with varying host defenses and post-infestation performances. We first characterized the prevalence and intensity of worm infestation in five snail hosts (Tegula pellisserpentis, Nerita scabricosta, N. funiculata, Planaxis planicostatus, and Cerithium stercusmuscarum). We then used manipulative experiments to test flatworm’s host choice, hosts’ behavioral rejection of flatworms, and hosts’ growth and survival following the infestation. In the field, flatworms were orders of magnitude more prevalent and dense in T. pellisserpentis, N. scabricosta, N. funiculata than P. planicostatus and C. stercusmuscarum, although the three former hosts were not necessarily more abundant. The results from our laboratory host selection trials mirrored these patterns; flatworms were 3 to 14 times more likely to choose T. pellisserpentis, N. scabricosta, N. funiculata over P. planicostatus and C. stercusmuscarum. The less preferred hosts frequently rejected flatworms via mantle contractions and foot withdrawals, which reduced the infestation rate by 39%−67%. These behaviors were less frequent or absent in the preferred hosts. Flatworm infestation variably influenced host performances in the field, negligibly affecting the growth and survival of T. pellisserpentis and N. funiculata but reducing the growth of P. planicostatus. Flatworms thus preferred less defended hosts that can also support higher worm densities without being harmed. Stable isotope analysis further revealed that flatworms are unlikely to feed on snail tissues and may live as a commensal in their preferred hosts. Our study demonstrates that host response traits can modulate a symbiont’s host choice and calls for more explicit considerations of host response variability in host preference research.

Host preferences of coexisting Perkinsea parasitoids during coastal dinoflagellate blooms

ABSTRACTParasites in aquatic systems are highly diverse and ubiquitous. In marine environments, parasite-host interactions contribute substantially to shaping microbial communities, but their nature and complexity remain poorly understood. In this study, we examined the relationship between Perkinsea parasitoids and bloom-forming dinoflagellate species. Our aim was to determine whether parasite-host species interactions are specific and whether the diversity and distribution of parasitoids are shaped by their dinoflagellate hosts. Several locations along the Catalan coast (NW Mediterranean Sea) were sampled during the blooms of five dinoflagellate species and the diversity of Perkinsea was determined by combining cultivation-based methods with metabarcoding of the V4 region of 18S rDNA. Most known species of Parviluciferaceae, and others not yet described, were detected, some of them coexisting in the same coastal location, and with a wide distribution. The specific parasite-host interactions determined for each of the studied blooms demonstrated the host preferences exhibited by parasitoids in nature. The dominance of a species within the parasitoid community is driven by the presence and abundances of its preferred host(s).The absence of parasitoid species, often associated with a low abundance of their preferred hosts, suggested that high infection rates are reached only under conditions that favour parasitoid propagation, especially dinoflagellate blooms.

Thick bark can protect trees from a severe ambrosia beetle attack

Thick bark has been shown to protect trees from wildfires, but can it protect trees from an ambrosia beetle attack? We addressed this question by examining the distribution of holes of the invasive Kuroshio Shot Hole Borer (KSHB, Euwallacea kuroshio; Coleoptera: Scolytinae) in the bark of Goodding’s black willow (Salix gooddingii), one of the KSHB’s most-preferred hosts. The study was conducted in the Tijuana River Valley, California, in 2016–17, during the peak of the KSHB infestation there. Using detailed measurements of bark samples cut from 27 infested trees, we tested and found support for two related hypotheses: (1) bark thickness influences KSHB attack densities and attack locations, i.e., the KSHB bores abundantly through thin bark and avoids boring through thick bark; and (2) bark thickness influences KSHB impacts, i.e., the KSHB causes more damage to thinner-barked trees than to thicker-barked trees. Our results indicate that thick bark protects trees because it limits the density of KSHB entry points and thereby limits internal structural damage to low, survivable levels. This is the first study to identify bark thickness as a factor that influences the density of KSHB—or any ambrosia beetle—in its host tree, and the first to link bark thickness to rates of host tree mortality.

Climate impacts on the vector capacity of tropical and temperate populations of the brown dog tick, Rhipicephalus sanguineus sensu lato.

The distribution and survival of a tick species are affected by several factors such as host availability, vegetation coverage, climatic conditions (humidity, photoperiod and temperature) and anthropic activities. This expert opinion discusses the differences between both tropical and temperate R. sanguineus lineages, how climate changes could affect their distribution and abundance, and consequently the incidence of the diseases transmitted by them to dogs, their preferred hosts.

Spatio-temporal variation of Mocis latipes (Guenée, 1852) (Lepidoptera: Erebidae) populations in Brazil according to meteorological factors

Mocis latipes (Guenée, 1852) (Lepidoptera: Erebidae) has been recognized as a major owlet caterpillar associated to the herbivory of gramineaceous plants across the American continent. During outbreaks, the caterpillars are capable of completely consuming preferred hosts (grasses) and, when these hosts are destroyed, they can move to adjacent non-grass plants and cause similar damage. Meteorological variable such as temperature and humidity are described as factors that affect the development and abundance of M. latipes. This paper aimed to describe and compare the spatial and temporal distribution of M. latipes in different locations in Brazil and to evaluate the influence of meteorological variables on the temporal range. A total of 12 locations were evaluated, in each collection point light traps were installed near cultivated areas. In order to understand the influence of meteorological variables on the abundance of M. latipes, the data were analyzed using a Generalized Linear Model according to Poisson regression. A linear regression was also used to verify the relation between the abundance and the latitude. A total of 1,985 moths were collected. The highest collections were in Amazon and Cerrado biomes. Results show that abundance was inversely related to increasing latitude and Poisson regression analysis indicated that the main meteorological variables were significantly related to abundance at each site. This study shows that due to the high preference for gramineas and the high temperature requirements (30°C), M. latipes is an important species in hot regions and regions with hight humidity. Furthurmore, even in higher latitudes, in subtropical areas, during summer months, populations can Rapidly growth being able to cause economic damages.

Ecology of Sandalwood (Santalum album L.) at Lingmethang, Eastern Bhutan

A study was carried out at Lingmethang to find out the ecological requirement for the growth of Sandalwood (Santalum album L.) trees in Bhutan. It also aimed to determine the preferred hosts of Sandalwood in the study site and to map its habitat suitability in the country. Plot size of 20 x 20 m2 for trees, 10 x 10 m2 for shrubs, and 5 x 5 m2 for regenerations and herbs were used. Soil samples were collected by digging soil to 25-30 cm depth from each plot. PC-ORD software was used for finding the relation of the variable with seedling abundance. A total of 19 tree species under 14 families and 40 undergrowth species under 24 families were recorded in the areas where Sandalwood is growing naturally. Mallotus philippensis and Albizia sikkimensis were the co-dominant tree species with chirpine as the dominant tree. Chromolaena odorata (Asteraceae) was the most preferred host species of the Sandalwood seedlings followed by Murraya koenigii. Mature Sandalwood tree was found parasitizing on Desmodium sp. (Fabaceae). Slope was one of the most determinant factors for the growth of Sandalwood (r = .951, p < .05), but rainfall had greater influence even though negative (r = -.943, p < .05) in the valley. Soil Nitrogen did not have much effect on the seedling abundance but mature trees prefered Fabaceae as hosts. A total of 16 dzongkhags are suitable for plantation of Sandalwood. Among these, Zhemgang Dzongkhag has the maximum potential area (469.62 km2) and Punakha Dzongkhag has the least (2.88 km2).

Subdividing the spectrum: quantifying host specialization in mistletoes

Parasites necessarily depend on their hosts, but the number of host species used by a parasite varies from one to hundreds. Estimating host range and identifying the preferred host species that influence distributional boundaries and confer greater advantage to the parasite has proven elusive. As well as the confounding effects of sampling effort, characterising host specificity and preference has been hindered by considering host-use without accounting for availability. We selected three mistletoe species (Lysiana exocarpi, Amyema quandang, and Amyema lucasii) and sampled mistletoe–host interactions and host availability free from sampling bias. To quantify host specificity and identify preferred host species we applied specialist/generalist scores (G) and resource selection ratios (ω) respectively. Host specificity and preference were assessed at four scales. The generalist L. exocarpi was found to parasitise 31 plant species. Even at small scales, G values and host species turnover were high, with eight preferred hosts identified. Amyema quandang had a low G score with significant preference for half of its Acacia hosts. Amyema lucasii significantly preferred one host, consequently having low G values at all scales. By collecting potential host data and applying G scores and ω, the parasite host spectrum can be quantitatively estimated rather than qualitatively described.