Non-native Host Research Articles

More than just the gene: investigating expression using a non-native plasmid and host and its impact on resistance conferred by β-lactamase OXA-58 isolated from a hospital wastewater microbiome.

With the escalation of hospital-acquired infections by multidrug resistant bacteria, understanding antibiotic resistance is of paramount importance. This study focuses on the β-lactamase gene, blaOXA-58, an important resistance determinant identified in a patient-facing hospital wastewater system. This study aimed to characterize the behaviour of the OXA-58 enzyme when expressed using a non-native plasmid and expression host. blaOXA-58 was cloned using a pET28a(+)/Escherichia coli BL21(DE3) expression system. Nitrocefin hydrolysis and antimicrobial susceptibility of OXA-58-producing cells were assessed against penicillin G, ampicillin, meropenem, and amoxicillin. blaOXA-58 conferred resistance to amoxicillin, penicillin G, and ampicillin, but not to meropenem. This was unexpected given OXA-58's annotation as a carbapenemase. The presence of meropenem also reduced nitrocefin hydrolysis, suggesting it acts as a competitive inhibitor of the OXA-58 enzyme. This study elucidates the phenotypic resistance conferred by an antimicrobial resistance gene (ARG) obtained from a clinically relevant setting and reveals that successful functional expression of ARGs is multifaceted. This study challenges the reliability of predicting antimicrobial resistance based solely on gene sequence alone, and serves as a reminder of the intricate interplay between genetics and structural factors in understanding resistance profiles across different host environments.

Identification of the mutual gliding locus as a factor for gut colonization in non-native bee hosts using the ARTP mutagenesis

BackgroundThe gut microbiota and their hosts profoundly affect each other’s physiology and evolution. Identifying host-selected traits is crucial to understanding the processes that govern the evolving interactions between animals and symbiotic microbes. Current experimental approaches mainly focus on the model bacteria, like hypermutating Escherichia coli or the evolutionary changes of wild stains by host transmissions. A method called atmospheric and room temperature plasma (ARTP) may overcome the bottleneck of low spontaneous mutation rates while maintaining mild conditions for the gut bacteria.ResultsWe established an experimental symbiotic system with gnotobiotic bee models to unravel the molecular mechanisms promoting host colonization. By in vivo serial passage, we tracked the genetic changes of ARTP-treated Snodgrassella strains from Bombus terrestris in the non-native honeybee host. We observed that passaged isolates showing genetic changes in the mutual gliding locus have a competitive advantage in the non-native host. Specifically, alleles in the orphan mglB, the GTPase activating protein, promoted colonization potentially by altering the type IV pili-dependent motility of the cells. Finally, competition assays confirmed that the mutations out-competed the ancestral strain in the non-native honeybee gut but not in the native host.ConclusionsUsing the ARTP mutagenesis to generate a mutation library of gut symbionts, we explored the potential genetic mechanisms for improved gut colonization in non-native hosts. Our findings demonstrate the implication of the cell mutual-gliding motility in host association and provide an experimental system for future study on host-microbe interactions.ArN8Xjm3N6Dubzus4DCSQmVideo

Reconstitution of the Early Stage of Chetomin Biosynthesis in Aspergillus fumigatus Leads to the Production of Epipolythiodioxopiperazines.

Using CRISPR-Cas9 technology and a microhomology-mediated end-joining repair system, we substituted genes of the gliotoxin pathway in Aspergillus fumigatus with genes responsible for chetomin biosynthesis from Chaetomium cochliodes, leading to the production of three new epipolythiodioxopiperazines (ETPs). This work represents the first successful endeavor to produce ETPs in a non-native host. Additionally, the simultaneous disruption of five genes in a single transformation marks the most extensive gene knockout event in filamentous fungi to date.

DIAZOTROPHIC ENDOPHYTE Klebsiella sp. N5 FROM SORGHUM SHOWS CROSS-COLONIZATION AND PLANT GROWTH PROMOTION IN RICE

Rice necessitates the highest levels of N fertilizers during its cultivation increasing demand for nitrogen fertilizers as well as negatively affecting the environment. Endophytic diazotrophic bacteria were isolated from sorghum, out of 35 isolates Klebsiella sp. N5 showed maximum potential for biological nitrogen fixation. Primary screening of strain N5 was done with acetylene reduction assay indicating dry root activity of 638.55 nmol C2H4 h-1 g-1. That was further confirmed by nifH gene amplification. The strain was identified morphologically, biochemically and 16S rDNA sequencing analysis and identified as Klebsiella sp. strain N5. This strain exhibited other plant growth-promoting (PGP) traits, such as phosphate solubilization, production of indole acetic acid, siderophore activity, ACC deaminase activity, and anti-fungal activity. PGP endophyte N5 was inoculated into rice seedlings to investigate its interaction under axenic conditions and to characterize its ability to colonize non-native host plant rice. Extensive colonization of rice roots was corroborated by Scanning electron microscopy. In-planta experiments with rice seeds inoculated with Klebsiella sp. N5 showed significant improvements in various agronomic traits such as increase in shoot length, root length, fresh and dry weight of root and shoot, chlorophyll content, and nitrogen content of the plant and soil compared to the untreated plants. Klebsiella sp. N5, a cross colonizer from sorghum (C4 plant) to rice (C3 plant) plays a crucial role in facilitating the acquisition of essential resources such as nitrogen, phosphorus, and iron through direct mechanisms. This study expands the horizon for its potential as a valuable bioinoculant for sustainable agricultural practices, particularly in non-native host rice, paving the way for future field trials.

Endoparasitic helminth fauna and diet of Geophagus sveni (Pisces) in Upper Paraná River basin.

In freshwater ecosystems, parasite infection patterns are influenced by factors including spatial-temporal variations, host diet, and habitat. Fish often change diets, affecting their parasite communities. This study focused on non-native host fish Geophagus sveni, aiming to characterize diet and endoparasitic helminth fauna patterns in the invaded area, investigating spatial and seasonal possible differences of endoparasite infections and correlating with host diet, in São José dos Dourados River and Tietê River areas. The host fish were collected in these areas during the dry and rainy season using gillnets. The endoparasites were collected and preserved in alcohol and identified using taxonomic methods, and stomach contents were examined for diet analysis. Parasitism descriptors were calculated and evaluated spatially and seasonally by ANOVA and the Kruskal-Wallis tests. PERMANOVA assessed G. sveni diet differences, and RDA correlated the endohelminth abundance with the host diet. Two endoparasites were recorded: metacercariae of Austrodiplostomum compactum (Trematoda) and larvae and adults of Raphidascaris (Sprentascaris) lanfrediae (Nematoda). Spatial differences were observed for the mean abundance and prevalence of R. (S.) lanfrediae and A. compactum prevalence. Seasonal variations of parasitic descriptors occurred for the nematode in the Tietê River area. The detritus and aquatic insects were the most consumed items by G. sveni. Detritus consumption positively correlates with nematode abundance. The findings indicate that factors such as artificial channels and rainfall, which can influence resource availability, may affect the fish's diet and potentially influence the structure of its endoparasite community. The study emphasizes the importance of understanding trophic chain-transmitted parasites and calls for further research in Neotropical environments.

Diversity and potential sources of introduction of the beech leaf nematode (Litylenchus crenatae mccannii) to Ontario, Canada

Litylenchus crenatae mccannii is a foliar nematode that causes severe damage to beech, known as beech leaf disease (BLD). Previous studies have characterized and identified L. crenataein Japan and a subspecies L. crenatae mccannii in the USA. Litylenchus crenatae mccannii has been found to cause BLD in native and non-native beech hosts in North America. As little is known about the distribution and diversity of the nematode in Ontario, Canada, beech foliage was sampled throughout southcentral Ontario. Incidence and severity maps show that BLD spread from its first detections in 2017, in Elgin and Norfolk counties, to the west and northeast. A gradient in severity and incidence was observed with the highest ratings at the locations where it was originally found. The extent of the nematode’s distribution is much broader than BLD, occurring throughout much of the range of American beech. Sequences of two barcoding loci for the L. crenatae mccannii isolates from 11 locations in Ontario showed 100% similarity within and among these locations. The genotype of L. crenatae mccannii found in Ontario is the same as that identified in the USA. This finding is consistent with the fact that 92% of beech imported into Canada is from the USA and suggests that the USA could be the origin of L. crenatae mccannii nematodes in Ontario or that both countries have imported beech trees from the same source country of BLD. This research provides motivation for further studies to clarify the sources of L. crenatae mccannii.

Invasion of Pieris mannii butterflies across Central Europe facilitated by urbanization

Urbanization progresses world-wide and the frequency of biological invasions increases. Understanding to what extent urban environments facilitate biological invasions and how this affects ecosystems within and outside urbanized areas thus becomes crucial. We here examine the role of urban environments in the invasion of the butterfly Pieris mannii that expanded across Central Europe within the last two decades. Using standardized butterfly captures at paired urban and (semi)natural field sites within the invaded range in Switzerland, we demonstrate that P. mannii is strongly associated with cities and towns. At least in some urban localities, this species is now the most common butterfly, and densities tend to be particularly high where urban areas are large. Because urban habitats commonly provide non-native host plants and perhaps also the physical structure and microclimate suitable to this butterfly, urbanization has clearly promoted the species’ rapid invasion. Studying phenology over an entire season, we further infer that P. mannii has up to six generations per year, which may allow the species to adjust its life cycle to changing season length during northward expansion. Overall, our study demonstrates how preadaptation to urbanized environments in a relatively specialized insect increases urban biodiversity on a large geographic scale.

Microbial host engineering for sustainable isobutanol production from renewable resources.

Due to the limited resources and environmental problems associated with fossil fuels, there is a growing interest in utilizing renewable resources for the production of biofuels through microbial fermentation. Isobutanol is a promising biofuel that could potentially replace gasoline. However, its production efficiency is currently limited by the use of naturally isolated microorganisms. These naturally isolated microorganisms often encounter problems such as a limited range of substrates, low tolerance to solvents or inhibitors, feedback inhibition, and an imbalanced redox state. This makes it difficult to improve their production efficiency through traditional process optimization methods. Fortunately, recent advancements in genetic engineering technologies have made it possible to enhance microbial hosts for the increased production of isobutanol from renewable resources. This review provides a summary of the strategies and synthetic biology approaches that have been employed in the past few years to improve naturally isolated or non-natural microbial hosts for the enhanced production of isobutanol by utilizing different renewable resources. Furthermore, it also discusses the challenges that are faced by engineered microbial hosts and presents future perspectives to enhancing isobutanol production. KEY POINTS: • Promising potential of isobutanol to replace gasoline • Engineering of native and non-native microbial host for isobutanol production • Challenges and opportunities for enhanced isobutanol production.

Host shift to non-native species or ecological dead end? Endangered branchiobdellidans (Annelida: Clitellata) found on introduced Signal Crayfish in Japan

Symbionts, including parasites, are usually small and thus have been overlooked for their existence and scientific research. In the context of biological invasion, host shifts between native and non-native species occur. Since symbionts often affect host behaviour and survival, it is important to reveal the cryptic invasions and host shifts of such small symbionts. Here, we report the first evidence of the potential host shift of a native endangered branchiobdellidans, ectosymbiotic crayfish worms, to a non-native Signal Crayfish, Pacifastacus leniusculus (Dana 1852), in Hokkaido, Japan. Pacifastacus leniusculus is native to North America and was recently introduced to the Atsubetsu River system in Sapporo. In addition to the North American ectosymbiont, Sathodrilus tetrodonta (Pierantoni, 1906), we found an endangered Japanese species, Cirrodrilus cirratus complex on P. leniusculus. However, C. cirratus complex as well as S. tetrodonta were not found on the native Japanese Crayfish, Cambaroides japonicus (De Haan, 1841), in the same river system, indicating a host shift of the ectosymbiont to invasive crayfish. It remains unclear whether C. cirratus complex will persist for a long time with the non-native host or if this is only a transient leading to local extinction.

Gene expression plasticity facilitates different host feeding in Ips sexdentatus (Coleoptera: Curculionidae: Scolytinae)

Host shift is ecologically advantageous and a crucial driver for herbivore insect speciation. Insects on the non-native host obtain enemy-free space and confront reduced competition, but they must adapt to survive. Such signatures of adaptations can often be detected at the gene expression level. It is astonishing how bark beetles cope with distinct chemical environments while feeding on various conifers. Hence, we aim to disentangle the six-toothed bark beetle (Ips sexdentatus) response against two different conifer defences upon host shift (Scots pine to Norway spruce). We conducted bioassay and metabolomic analysis followed by RNA-seq experiments to comprehend the beetle’s ability to surpass two different terpene-based conifer defence systems. Beetle growth rate and fecundity were increased when reared exclusively on spruce logs (alternative host) compared to pine logs (native host). Comparative gene expression analysis identified differentially expressed genes (DEGs) related to digestion, detoxification, transporter activity, growth, signalling, and stress response in the spruce-feeding beetle gut. Transporter genes were highly abundant during spruce feeding, suggesting they could play a role in pumping a wide variety of endogenous and xenobiotic compounds or allelochemicals out. Trehalose transporter (TRET) is also up-regulated in the spruce-fed beetle gut to maintain homeostasis and stress tolerance. RT-qPCR and enzymatic assays further corroborated some of our findings. Taken together, the transcriptional plasticity of key physiological genes plays a crucial role after the host shift and provides vital clues for the adaptive potential of bark beetles on different conifer hosts.

Novel host plant use by a specialist insect depends on geographic variation in both the host and herbivore species

Understanding the circumstances under which insect herbivores will adopt a novel host plant is a longstanding question in basic and applied ecology. While geographic variation in host use can arise through differences in both herbivore preference and plant characteristics, there is a tendency to attribute geographic variation in host use to regional differences in herbivore preference alone. This is especially true for herbivores specialized to one or a few plant species. We compared how geographic variation in herbivore preference and host plant origin shape regional differences in host plant use by the specialized herbivore, Euphydryas phaeton. In parts of its range, E. phaeton uses only a native host, Chelone glabra, while in others, it also uses an introduced host, Plantago lanceolata. We offered female butterflies from each region the non-native host plant sourced from both regions and compared their oviposition behavior. The non-native host was almost universally rejected by butterflies in the region where only the native plant is used. In the region where butterflies use both hosts, females accepted non-native plants from their natal region twice as often as non-native plants from the other region where they are not used. Acceptance differed substantially among individual butterflies within regions but not among plants within regions. Thus, both individual preference and regional differences in both the insect and non-native host contributed to the geographic variation in different ways. These results highlight that, in addition to herbivore preference, regional differences in perceived plant suitability may be an important driver of diet breadth.

Delineating the calling pattern of Oecanthus indicus from native and non-native plant species.

The study attempted to understand the effect of the host plants on the call parameters of native tree cricket, Oecanthus indicus (Order: Orthoptera, Sub-order: Ensifera, Family: Gryllidae) while calling from native (Justicia adhatoda) and non-native host plant species (Lantana camara and Hyptis suaveolens). The study was conducted at four locations across India. Calls of O. indicus were recorded on these host plants in the field and spectral and temporal parameters of calls were analysed. The results suggested that the peak frequency varied among the two non-native plant species while the difference in temporal pattern between the native and non-native host plants was observed only in the syllable period. The study also quantified the choice of calling positions of insects from the three-host species. The native O. indicus chose non-native H. suaveolens leaves extensively as a preferable site to baffle (37%). Differences in the call parameters and choice of the host plant by insects may ultimately affect the preference and performance of insects on invasive plants. The study would aid in exploring the underlying evolutionary and ecological processes of adaptive success of insects on non-native plants.

A Method for Identification of Biotype-Specific Salivary Effector Candidates of Aphid.

Polyphagous aphids often consist of host-specialized biotypes that perform poorly in non-native hosts. The underlying mechanisms remain unknown. Host-specialized biotypes may express biotype-specific salivary effectors or elicitors that determine aphid hosts. Here, we tried three strategies to identify possible effectors in Malvaceae- (MA) and Cucurbitaceae-specialized (CU) biotypes of the cotton-melon aphid Aphis gossypii Glover. The whole-aphid RNA-seq identified 765 differentially expressed genes (DEGs), and 139 of them were possible effectors; aphid-head RNA-seq identified 523 DEGs were identified, and 98 of them were possible effectors. The homologous genes of published aphid effectors were not differentially expressed between CU and MA. Next, quantitative proteomic analyses of saliva identified 177 possible proteins, and 44 of them were different proteins. However, none of the genes of the 44 proteins were differentially expressed, reflecting the discrepancy between transcriptome and proteome data. Finally, we searched for DEGs of the 177 salivary proteins in the aphid-head transcriptomes, and the salivary proteins with expression differences were regarded as effector candidates. Through this strategy, 11 effector candidates were identified, and their expression differences were all confirmed by RT-qPCR. The combinatorial analysis has great potential to identify biotype-specific effector candidates in aphids and other sap-sucking insects.

Regulatory response to a hybrid ancestral nitrogenase in Azotobacter vinelandii.

Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs. IMPORTANCE Azotobacter vinelandii is a key model bacterium for the study of biological nitrogen fixation, an important metabolic process catalyzed by nitrogenase enzymes. Here, we demonstrate that compatibilities between engineered A. vinelandii strains and nitrogenase variants can be modulated at the regulatory level. The engineered strain studied here responds by adjusting the expression of proteins involved in cellular processes adjacent to nitrogen fixation, rather than that of nitrogenase proteins themselves. These insights can inform future strategies to transfer nitrogenase variants to non-native hosts.

Parasitic Helminths and Freshwater Fish Introduction in Europe: A Systematic Review of Dynamic Interactions

The introduction of non-native freshwater fish is a primary cause of aquatic biodiversity loss at global scale. Such introductions have a severe impact on freshwater ecosystems in terms of competition, predation, habitat alteration, genetic pollution and transmission of diseases and parasites. A systematic review was conducted on the helminths parasites of freshwater fish in the context of species introduction and a total of 199 publications were retrieved between 1969 and November 2022. Several scenarios may arise when a new fish species arrive in a recipient area. Non-native fish hosts can co-introduce their parasites without transmitting them to native fish (e.g., the case of North American Centrarchidae and their Monogenea parasites). Another possible outcome is the transfer of these parasites to the native fish fauna (spillover, e.g., the cases of the Nematoda Anguillicola crassus Kuwahara, Niimi & Itagaki, 1974 and the Monogenea Gyrodactylus salaris Malmberg, 1957). Reciprocally, non-native fish hosts may acquire parasites in their new distribution range whether these parasites are native or were previously introduced (e.g., the cases of Ponto-Caspian Gobiidae and the Chinese sleeper Perccottus glenii Dybowski, 1877). Acquired parasites can then be spilled back to the native fauna. This phenomenon is of particular interest when non-native fish hosts influence the dynamics of zoonotic parasites.

High-impact practices (HIPs) benefits from study abroad country agent: a multi-method multi-perspective approach

PurposeThe purpose of this study is to extend the Blevins et al. (2020) study by empirically examining the benefits of using a customized study abroad host-country provider (hereafter referred to as “SAA”) of logistical and other services that support non-native host country (hereafter referred to as non-indigenous) college of business study abroad educators. This study also makes a significant contribution by extending Strange and Gibson’s (2017) call by examining transformative learning experiences (TLEs), a high-impact practice, from educators’ and students’ perspectives of two types of study abroad experiences (i.e. one with and one without an SAA).Design/methodology/approachA mixed methods and multiple perspectives triangulation of the three studies (i.e. student survey, student-produced artifacts data and faculty interviews conducted in Canada, Spain and the UK) was used for this study to increase confidence in the findings by providing a comprehensive picture of the results. A mixed methodology provides rich, in-depth data for analysis as to how study abroad experience [hereafter referred to as experience(s) abroad] benefits from contracting with an SAA to work with a non-indigenous business course educator.FindingsThis study's findings demonstrate the positive impact of transformative learning from a short-term study abroad experience from contracting with an SAA.Practical implicationsBenefits of contracting with a host-country SAA are increased time and a reduction in the emotional toll on educators. Educators are free to provide memorable international business educational experiences abroad, resulting in student satisfaction and transformative learning.Originality/valueThe originality of this study is the mixed methods and multiple perspectives approach to the topic.

Successful colonization of novel spruce hosts by European and North American spruce bark beetles can favour trans-Atlantic range expansion

Abstract The European spruce bark beetle Ips typographus and the North American spruce beetle Dendroctonus rufipennis cause high mortality of spruces on their native continents. Both species have been inadvertently transported beyond their native ranges. With similar climates and the presence of congeneric spruce hosts in Europe and North America, there is a risk that one or both bark beetle species become established into the non-native continent. There are many challenges that an introduced population of bark beetles would face, but an important prerequisite for establishment is the presence of suitable host trees. We tested the suitability of non-native versus native hosts by exposing cut bolts of Norway spruce (Picea abies), black spruce (Picea mariana) and white spruce (Picea glauca) to beetle attacks in the field in Norway and Canada. We quantified attack density, brood density and reproductive success of I. typographus and D. rufipennis in the three host species. We found that I. typographus attacked white and black spruce at comparable densities to its native host, Norway spruce, and with similar reproductive success in all three host species. In contrast, D. rufipennis strongly preferred to attack white spruce (a native host) but performed better in the novel Norway spruce host than it did in black spruce, a suboptimal native host. Our results suggest that I. typographus will find abundant and highly suitable hosts in North America, while D. rufipennis in Europe may experience reduced reproductive success in Norway spruce.

Additive and interactive effects of anthropogenic stressors on an insect herbivore.

The pressures of global change acting on wild plants and animals include exposure to environmental toxins, the introduction of non-native species, and climate change. Relatively few studies have been reported in which these three main classes of stressors have been examined simultaneously, allowing for the possibility of synergistic effects in an experimental context. In this study, we exposed caterpillars of the Melissa blue butterfly (Lycaeides melissa) to three concentrations of chlorantraniliprole, under three experimental climates, on a diet of a native or a non-native host plant throughout larval development in a fully factorial experiment. We find that high pesticide exposure and a non-native diet exhibit strong negative effects on caterpillars, resulting in 62% and 42% reduction in survival, respectively, while interactive effects tend to be weaker, ranging from 15% to 22% reduction in survival. Interactive effects have been shown to be strong in other contexts, but do not appear to be universal; however, our study shows that the cumulative effects of stressors acting in isolation (additively) are sufficiently strong to severely reduce survival and by extension population persistence in the wild.

Beneficial effects of selected rhizospheric and endophytic bacteria, inoculated individually or in combination, on non-native host plant development

Plant beneficial bacteria have been traditionally inoculated as unique strains, although combining bacteria with complementary traits could maximize their positive effect on plant growth and development. Our objective was to elaborate consortia from selected rhizospheric and endophytic bacteria with antifungal and plant growth promoting properties, and evaluate their beneficial effects on the growth of Physalis ixocarpa, an annual native Mexican species of horticultural importance. Bacterial strains were selected based on their antifungal activity against Fusarium spp. through in vitro antagonism assays. Characterization of the profile of volatile organic compounds (VOC) of newly-identified endophytic strains able to significantly inhibit Fusarium spp. evidenced the presence of sulfur compounds and ketones, reported for their antifungal activity. Seven bacterial strains were able to solubilize phosphate on NBRIP medium. Their capacity to promote the growth of A. thaliana in vitro was further tested. All stains stimulated the formation of lateral roots and root hairs, and enhanced A. thaliana biomass, most likely through auxin production. Twelve consortia were elaborated from rhizospheric and root endophytic bacteria, and the effects of consortia and individual strain inoculation on the growth and development of P. ixocarpa were evaluated in a greenhouse trial. Rhizobacterial strains A8a and 5911, and consortia formed by A8a + B3R7 and SO + B3R7 (all belonging to the Bacillus genus) showed the best results in terms of growth promotion and floral onset, with increases in plant height by up to 45% and flowering beginning 30 days before than in the Control. Our results confirm the potential of combining rhizospheric and endophytic bacteria with multiple beneficial traits for enhancing plant development and suggest that the most promising bacterial treatments could be applied to avocado trees, their natural host, to foster their productivity.

EFL STUDENTS’ VOICES ON NATIVE SPEAKER PRESENTERS ON YOUTUBE VIDEOS AND THEIR IMPACT ON STUDENTS’ ENGLISH COMPETENCY DEVELOPMENT

There have been many studies on YouTube and its advantages for learning English, yet a specific research on students’ perception of native speaker presenters is still rare. This study aimed to investigate students’ general perspectives on YouTube videos, and exploring students’ perspectives on YouTube video presenters/hosts (native speaker and non-native speaker), and how they positively affect students’ English competency. A descriptive analysis method was done by distributing a questionnaire written in Indonesian via Google form to 156 respondents. The result of questionnaire was then analysed qualitatively using Jeffreys’s Amazing Statistics Program (JASP) 0.14.1. A semi-structured interview to ten respondents to dig out more about their response for certain items or questions was also done. The analysis revealed that YouTube provides a wide variety of topics, available in multiple languages, and might be downloaded anytime. When the presenters are the native ones, the respondents got some positive impacts in improving their English competency. Students felt challenged in building their understanding of the content, could practice their listening skill correctly, may train and improve their speaking skill, got new English vocabulary, learn to pause, stress, and use appropriate intonations in uttering words, sentences, and phrases, could practice proper use of grammar, identify people’s live and behave, increase students’ general knowledge, increase their knowledge of English language culture, and they become more creative. However, some respondents preferred the non-native hosts since they tend to speak slower and sometimes switch to Indonesian that facilitates the respondents understanding.