Bacterial Gene Transfer Research Articles

Microplastic biofilms promote the horizontal transfer of antibiotic resistance genes in estuarine environments

As emerging pollutants, microplastics can aggregate microorganisms on their surfaces and form biofilms, enriching antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Consequently, microplastic biofilms have become a focal point of research. Horizontal gene transfer is one of the primary mechanisms by which bacteria acquire antibiotic resistance, with much of the research focusing on suspended bacteria. However, microplastic biofilms, as hotspots for horizontal gene transfer, also merit significant investigation. This study primarily explored and compared the frequency of ARG conjugative transfer between suspended bacteria and microplastic biofilms. The results demonstrated that, compared to suspended bacteria, microplastic biofilms enhanced the frequency of ARG conjugative transfer by 7.2–19.6 times. Among them, biofilms on polyethylene microplastics showed the strongest promotion of conjugation. After the formation of microplastic biofilms, there was a significant increase in bacterial density within the biofilms, which raised the collision frequency of donor and recipient bacteria. Then microplastic biofilms facilitated the gene expression levels of outer membrane proteins, enhanced bacterial gene transfer capabilities, promoted the synthesis of conjugative pili, accelerated the formation of conjugative pairing systems, and elevated the expression levels of genes related to DNA replication and transfer systems, thereby enhancing the conjugative transfer of ARGs within microplastic biofilms. Among different types of microplastic biofilms, polyethylene biofilms exhibited the highest bacterial density, thus showing the highest frequency of ARG conjugation. This study highlights the risks associated with ARG conjugative transfer following the formation of microplastic biofilms and provides insights into the risks of microplastic and antibiotic resistance propagation in estuarine environments.

Leveraging the potential of bacterial lateral gene transfer in boosting the efficacy of an edible probiotic prototype yogurt vaccine for COVID-19

Administration of coronavirus disease-2019 (COVID-19) vaccines with appropriate booster doses through painful injections under clinical supervision was challenging during the recent COVID-19 pandemic. As an alternative solution, we designed a safer, edible probiotic yogurt vaccine prototype (YoVac) that can be orally consumed by circumventing painful injections and clinical supervision. We hypothesized that YoVac prepared using Lactobacillus carrying an antigen coding gene (donor) can transfer the same to other bacteria (recipients) in the human gut microbiome (hgMb) through lateral gene transfer (LGT) for boosted antigen levels potentially triggering a robust immune response. In this study we confirmed the in vitro LGT efficiency of a plasmid (pRBD-Ampr) containing severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) spike protein-receptor binding domain (RBD) coding gene along with an ampicillin-resistance gene (selection marker) from the probiotic Lactobacillus (donor) cultured from homemade yogurt to E. coli and Helicobacter pylori (recipients). Both the donor and recipient bacteria not only exhibited ampicillin-resistance from pRBD-Ampr but also expressed RBD protein. Furthermore, Lactobacillus isolated from YoVac consistently showed the expression of RBD protein over a period of one month confirming the shelf life of our prototype stored at 4 °C. Taken together, our in vitro results provide a preliminary basis for the potential in vivo transfer of RBD coding gene from YoVac to other bacterial species in the hgMb through LGT and may potentially boost the vaccine dosage by delegating them.

Mobile genetic elements define the non-random structure of the Salmonella enterica serovar Typhi pangenome.

Bacterial relatedness measured using select chromosomal loci forms the basis of public health genomic surveillance. While approximating vertical evolution through this approach has proven exceptionally valuable for understanding pathogen dynamics, it excludes a fundamental dimension of bacterial evolution-horizontal gene transfer. Incorporating the accessory genome is the logical remediation and has recently shown promise in expanding epidemiological resolution for enteric pathogens. Employing k-mer-based Jaccard index analysis, and a novel genome length distance metric, we computed pangenome (i.e., core and accessory) relatedness for the globally important pathogen Salmonella enterica serotype Typhi (Typhi), and graphically express both vertical (homology-by-descent) and horizontal (homology-by-admixture) evolutionary relationships in a reticulate network of over 2,200 U.S. Typhi genomes. This analysis revealed non-random structure in the Typhi pangenome that is driven predominantly by the gain and loss of mobile genetic elements, confirming and expanding upon known epidemiological patterns, revealing novel plasmid dynamics, and identifying avenues for further genomic epidemiological exploration. With an eye to public health application, this work adds important biological context to the rapidly improving ways of analyzing bacterial genetic data and demonstrates the value of the accessory genome to infer pathogen epidemiology and evolution.IMPORTANCEGiven bacterial evolution occurs in both vertical and horizontal dimensions, inclusion of both core and accessory genetic material (i.e., the pangenome) is a logical step toward a more thorough understanding of pathogen dynamics. With an eye to public, and indeed, global health relevance, we couple contemporary tools for genomic analysis with decades of research on mobile genetic elements to demonstrate the value of the pangenome, known and unknown, annotated, and hypothetical, for stratification of Salmonella enterica serovar Typhi (Typhi) populations. We confirm and expand upon what is known about Typhi epidemiology, plasmids, and antimicrobial resistance dynamics, and offer new avenues of exploration to further deduce Typhi ecology and evolution, and ultimately to reduce the incidence of human disease.

Coexistence of multidrug resistance and ESBL encoding genes - blaTEM, blaSHV, and blaCTX-M; its amplification and dispersion in the environment via municipal wastewater treatment plant

Municipal wastewater treatment plants (MWWTPs) are a global source of antibiotic resistance genes (ARGs), collecting wastewater from a variety of sources, including hospital wastewater, domestic wastewater, runoff from agricultural and livestock farms, etc. These sources are contaminated with organic and inorganic pollutants, ARGs and antibiotic-resistant bacteria (ARB). Such pollutants aided eutrophication and encouraged bacterial growth. During bacterial growth horizontal gene transfer (HGT) and vertical gene transfer (VGT) of ARGs and extended-spectrum β-lactamase (ESBL) encoding genes may facilitate, resulting in the spread of antibiotic resistance exponentially. The current study investigated the prevalence of multidrug resistance (MDR) and ESBL encoding genes in various treatment units of MWWTP and their spread in the environment. A total of three sampling sites (BUT, BRO, and BFB) were chosen, and 33 morphologically distinct bacterial colonies were isolated. 14 of the 33 isolates tested positive for antibiotic resistance and were further tested for the coexistence of MDR and ESBL production. The selected 14 isolates showed the highest resistance to trimethoprim (85.71%), followed by ciprofloxacin, azithromycin, and ampicillin (71.42%), tetracycline (57.14%), and vancomycin, gentamicin, and colistin sulphate (50%). A total of 9 isolates (64.28%) were phenotypically positive for ESBL production (BUT2, BUT3, BUT5, BRO1, BRO2, BRO3, BRO4, BRO5 and BFB1). The molecular detection of ESBL encoding genes, i.e. blaTEM, blaSHV, and blaCTX-M was carried out. The most prevalent gene was blaTEM (69.23%), followed by blaSHV (46.15%), and blaCTX-M (23.07%). In this study, 9 isolates (64.28%) out of 14 showed the coexistence of MDR and ESBL encoding genes, namely BUT3, BUT4, BUT5, BUT6, BUT7, BRO1, BRO2, BRO4, and BFB1. The coexistence of ESBL encoding genes and resistance to other antibiotic classes exacerbates human health and the environment.

Horizontal gene transfer in plant microbiomes: integrons as hotspots for cross-species gene exchange.

Plant microbiomes play important roles in plant health and fitness. Bacterial horizontal gene transfer (HGT) can influence plant health outcomes, driving the spread of both plant growth-promoting and phytopathogenic traits. However, community dynamics, including the range of genetic elements and bacteria involved in this process are still poorly understood. Integrons are genetic elements recently shown to be abundant in plant microbiomes, and are associated with HGT across broad phylogenetic boundaries. They facilitate the spread of gene cassettes, small mobile elements that collectively confer a diverse suite of adaptive functions. Here, we analysed 5,565 plant-associated bacterial genomes to investigate the prevalence and functional diversity of integrons in this niche. We found that integrons are particularly abundant in the genomes of Pseudomonadales, Burkholderiales, and Xanthomonadales. In total, we detected nearly 9,000 gene cassettes, and found that many could be involved in plant growth promotion or phytopathogenicity, suggesting that integrons might play a role in bacterial mutualistic or pathogenic lifestyles. The rhizosphere was enriched in cassettes involved in the transport and metabolism of diverse substrates, suggesting that they may aid in adaptation to this environment, which is rich in root exudates. We also found that integrons facilitate cross-species HGT, which is particularly enhanced in the phyllosphere. This finding may provide an ideal opportunity to promote plant growth by fostering the spread of genes cassettes relevant to leaf health. Together, our findings suggest that integrons are important elements in plant microbiomes that drive HGT, and have the potential to facilitate plant host adaptation.

Effect of Temperature on Carbapenemase-Encoding Plasmid Transfer in Klebsiella pneumoniae.

Bacteria causing human infections can develop antibiotic resistance due to various factors. Temperature affects bacterial growth and gene transfer; however, studies exploring the association between the changes in local temperature and antibiotic resistance are limited. Here, we investigated the effects of local temperatures on the distribution of antibiotic resistance and transmission of carbapenemase-producing Enterobacterales using the data on Klebsiella pneumoniae from sentinel hospitals in eight regions included in the Korea Global Antimicrobial Resistance Surveillance System between 2017 and 2021. The resistance rates to most antibiotics, including carbapenems, varied significantly according to local temperature (p < 0.047), except for aminoglycosides. Conjugation experiments at various temperatures for strains encoding the carbapenemase gene on a plasmid revealed significant variation in the optimal conjugation temperatures for plasmids carrying blaKPC and blaNDM genes. The optimal conjugation temperatures demonstrating the highest stability for blaKPC- and blaNDM-carrying plasmids were 25 °C (p = 0.030) and 30 °C (p = 0.007), respectively. The stability of blaKPC-IncF was higher at 25 °C than that at 30 °C (p = 0.032) or 37 °C (p = 0.047), while blaKPC-IncX3 exhibited the lowest stability at 37 °C (p = 0.047). blaNDM-IncX3 was more stable at 30 °C than at 37 °C (p = 0.049). These findings suggest that the optimal temperature for carbapenemase gene transmission varied between 25 °C and 30 °C, indicating that warmer seasons promote the transfer of more antibiotic resistance-related genes and highlighting the importance of local temperature in the spread and transmission of plasmids carrying carbapenemases.

Fermented Foods as a Potential Vehicle of Antimicrobial-Resistant Bacteria and Genes

Fermented food products are widely consumed for their nutritional and health-promoting properties, earning them a central place in diets around the globe. However, these foods can present a paradox, as they have the potential to harbor not only beneficial probiotics but also antibiotic-resistant (AR) microbes and genes. The impact of AR microbes and genes in fermented foods has far-reaching implications, such as potential effects on human health, repercussions in the food industry, and environmental consequences. An in-depth analysis of AR microbes and genes in fermented foods, including dairy products, fermented fruits and vegetables, meat products, and beverages, would provide insights into the extent and ramifications of the issue with these foods. Therefore, this review systematically presents the status of AR in fermented foods, with a particular focus on AR bacteria and genes within this category of food products. The review also highlights the complexities of AR in fermented foods, emphasizing the role of bacterial adaptation during the fermentation process and the dynamics of bacterial gene transfer. Various factors contributing to AR microbes and genes are brought into focus, including intrinsic resistance among bacteria in fermented foods and the potential risk of contamination with pathogenic bacteria. Moreover, this review presents a range of mitigation strategies, from the development of novel antimicrobials to advances in fermentation technology and regulatory control. This comprehensive perspective on the intricate interplay between AR and fermented food will potentially pave the way for more targeted research and mitigation strategies in this critical area.

Effect of resistance difference on distribution of antibiotics in bacterial cell and conjugative gene transfer risks during electrochemical flow through reaction

The occurrences and spread of antibiotic resistance (AR) mediated by horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs) in aquatic environment have been aggravated because of the abuse of antibiotics. While the pressure of different antibiotics is known to induce the spread of AR in bacteria, whether distribution of different antibiotics in cell structure could affect HGT risks is not clear. Here, a significant difference between the distribution of tetracycline hydrochloride (Tet) and sulfamethoxazole (Sul) in cell structure during electrochemical flow through reaction (EFTR) process was firstly reported. Meanwhile, EFTR treatment possessed excellent disinfection performance and consequently controlled the HGT risks. The intracellular Tet (iTet) was discharged through efflux pumps to increase the content of extracellular Tet (eTet) due to the resistance of donor E. coli DH5α under the selective pressure of Tet, declining the damage of donor and plasmid RP4. The HGT frequency was 8.18-fold increase compared with that by EFTR treatment alone. While the secretion of intracellular Sul (iSul) was inhibited by blocking the formation of efflux pumps to inactivate the donor under the Sul pressure, and the total content of iSul and adsorbed Sul (aSul) to be 1.36-fold higher than that of eSul. Therefore, the reactive oxygen species (ROS) generation and cell membrane permeability were improved to release ARGs, and •OH attacked plasmid RP4 in the EFTR process, inhibiting the HGT risks. This study advances the awareness of the interaction between distribution of different antibiotics in cell structure and the HGT risks in the EFTR process.

Archaeal Host Cell Recognition and Viral Binding of HFTV1 to Its Haloferax Host.

Viruses are highly abundant and the main predator of microorganisms. Microorganisms of each domain of life are infected by dedicated viruses. Viruses infecting archaea are genomically and structurally highly diverse. Archaea are undersampled for viruses in comparison with bacteria and eukaryotes. Consequently, the infection mechanisms of archaeal viruses are largely unknown, and most available knowledge stems from viruses infecting a select group of archaea, such as crenarchaea. We employed Haloferax tailed virus 1 (HFTV1) and its host, Haloferax gibbonsii LR2-5, to study viral infection in euryarchaea. We found that HFTV1, which has a siphovirus morphology, is virulent, and interestingly, viral particles adsorb to their host several orders of magnitude faster than most studied haloarchaeal viruses. As the binding site for infection, HFTV1 uses the cell wall component surface (S)-layer protein. Electron microscopy of infected cells revealed that viral particles often made direct contact with their heads to the cell surface, whereby the virion tails were perpendicular to the surface. This seemingly unfavorable orientation for genome delivery might represent a first reversible contact between virus and cell and could enhance viral adsorption rates. In a next irreversible step, the virion tail is orientated toward the cell surface for genome delivery. With these findings, we uncover parallels between entry mechanisms of archaeal viruses and those of bacterial jumbo phages and bacterial gene transfer agents. IMPORTANCE Archaeal viruses are the most enigmatic members of the virosphere. These viruses infect ubiquitous archaea and display an unusually high structural and genetic diversity. Unraveling their mechanisms of infection will shed light on the question if entry and egress mechanisms are highly conserved between viruses infecting a single domain of life or if these mechanisms are dependent on the morphology of the virus and the growth conditions of the host. We studied the entry mechanism of the tailed archaeal virus HFTV1. This showed that despite "typical" siphovirus morphology, the infection mechanism is different from standard laboratory models of tailed phages. We observed that particles bound first with their head to the host cell envelope, and, as such, we discovered parallels between archaeal viruses and nonmodel bacteriophages. This work contributes to a better understanding of entry mechanisms of archaeal viruses and a more complete view of microbial viruses in general.

UV-aging of microplastics increases proximal ARG donor-recipient adsorption and leaching of chemicals that synergistically enhance antibiotic resistance propagation

Despite growing attention to environmental pollution by microplastics (MP), the effects of MP aging on bacterial horizontal gene transfer (HGT) have not been systematically investigated. Here, we used UV-aged polystyrene microplastics (PS-MPs) to investigate how aging affects antibiotic resistance genes (ARGs) transfer efficiency from various ARG vectors to recipient bacteria. The adsorption capacity of MP20 (20-day UV-aged PS-MPs) towards E. coli (harboring plasmid-borne blaTEM-1), plasmid pET29 (harboring blaNDM-1) and phage lambda (carrying the aphA1 ARG) increased by 6.6-, 5.2- and 8.3-fold, respectively, relative to pristine PS-MPs (MP0), due to increased specific surface area and affinity for these ARG vectors. Moreover, MP20 released more organic compounds (TOC 1.6 mg/g-MP20, versus 0.2 mg/g-MP0 in 4 h) –possibly depolymerization byproducts (verified by GC-MS), which induced intracellular ROS generation, increased cell permeability and upregulated HGT associated genes. Accordingly, MP20 enhanced ARG transfer frequency from E. coli, plasmid pET29 and phage lambda (relative to MP0) by 1.3-, 4.7- and 3.5-fold, respectively. The Bliss independence model infers that higher bacterial adsorption and exposure to chemicals released during MP aging synergistically enhanced ARG transfer. This underscores the need to assess the significance of this overlooked phenomenon to the environmental dissemination of antibiotic resistance and other HGT processes.

Bacterial chromosomal mobility via lateral transduction exceeds that of classical mobile genetic elements

It is commonly assumed that the horizontal transfer of most bacterial chromosomal genes is limited, in contrast to the frequent transfer observed for typical mobile genetic elements. However, this view has been recently challenged by the discovery of lateral transduction in Staphylococcus aureus, where temperate phages can drive the transfer of large chromosomal regions at extremely high frequencies. Here, we analyse previously published as well as new datasets to compare horizontal gene transfer rates mediated by different mechanisms in S. aureus and Salmonella enterica. We find that the horizontal transfer of core chromosomal genes via lateral transduction can be more efficient than the transfer of classical mobile genetic elements via conjugation or generalized transduction. These results raise questions about our definition of mobile genetic elements, and the potential roles played by lateral transduction in bacterial evolution.

Mechanisms of Transforming DNA Uptake to the Periplasm of Bacillus subtilis.

ABSTRACTWe demonstrate here that the acquisition of DNase resistance by transforming DNA, often assumed to indicate transport to the cytoplasm, reflects uptake to the periplasm, requiring a reevaluation of conclusions about the roles of several proteins in transformation. The new evidence suggests that the transformation pilus is needed for DNA binding to the cell surface near the cell poles and for the initiation of uptake. The cellular distribution of the membrane-anchored ComEA of Bacillus subtilis does not dramatically change during DNA uptake as does the unanchored ComEA of Vibrio and Neisseria. Instead, our evidence suggests that ComEA stabilizes the attachment of transforming DNA at localized regions in the periplasm and then mediates uptake, probably by a Brownian ratchet mechanism. Following that, the DNA is transferred to periplasmic portions of the channel protein ComEC, which plays a previously unsuspected role in uptake to the periplasm. We show that the transformation endonuclease NucA also facilitates uptake to the periplasm and that the previously demonstrated role of ComFA in the acquisition of DNase resistance derives from the instability of ComGA when ComFA is deleted. These results prompt a new understanding of the early stages of DNA uptake for transformation.

Were eukaryotes made by sex?: Sex might have been vital for merging endosymbiont and host genomes giving rise to eukaryotes.

I hypothesize that the appearance of sex facilitated the merging of the endosymbiont and host genomes during early eukaryote evolution. Eukaryotes were formed by symbiosis between a bacterium that entered an archaeon, eventually giving rise to mitochondria. This entry was followed by the gradual transfer of most bacterial endosymbiont genes into the archaeal host genome. I argue that the merging of the mitochondrial genes into the host genome was vital for the evolution of genuine eukaryotes. At the time this process commenced it was unprecedented and required a novel mechanism. I suggest that this mechanism was meiotic sex, and that its appearance might have been THE crucial step that enabled the evolution of proper eukaryotes from early endosymbiont containing proto-eukaryotes. Sex might continue to be essential today for keeping genome insertions in check. Also see the video abstract here: https://youtu.be/aVMvWMpomac.

Jekyll or Hyde? The genome (and more) of Nesidiocoris tenuis, a zoophytophagous predatory bug that is both a biological control agent and a pest.

Nesidiocoris tenuis (Reuter) is an efficient predatory biological control agent used throughout the Mediterranean Basin in tomato crops but regarded as a pest in northern European countries. From the family Miridae, it is an economically important insect yet very little is known in terms of genetic information and no genomic or transcriptomic studies have been published. Here, we use a linked‐read sequencing strategy on a single female N. tenuis. From this, we assembled the 355 Mbp genome and delivered an ab initio, homology‐based and evidence‐based annotation. Along the way, the bacterial “contamination” was removed from the assembly. In addition, bacterial lateral gene transfer (LGT) candidates were detected in the N. tenuis genome. The complete gene set is composed of 24 688 genes; the associated proteins were compared to other hemipterans (Cimex lectularis, Halyomorpha halys and Acyrthosiphon pisum). We visualized the genome using various cytogenetic techniques, such as karyotyping, CGH and GISH, indicating a karyotype of 2n = 32. Additional analyses include the localization of 18S rDNA and unique satellite probes as well as pooled sequencing to assess nucleotide diversity and neutrality of the commercial population. This is one of the first mirid genomes to be released and the first of a mirid biological control agent.

Distribution of RecBCD and AddAB recombination-associated genes among bacteria in 33 phyla

Homologous recombination plays key roles in fundamental processes such as recovery from DNA damage and in bacterial horizontal gene transfer, yet there are still open questions about the distribution of recognized components of recombination machinery among bacteria and archaea. RecBCD helicase-nuclease plays a central role in recombination among Gammaproteobacteria like Escherichia coli; while bacteria in other phyla, like the Firmicute Bacillus subtilis, use the related AddAB complex. The activity of at least some of these complexes is controlled by short DNA sequences called crossover hotspot instigator (Chi) sites. When RecBCD or AddAB complexes encounter an autologous Chi site during unwinding, they introduce a nick such that ssDNA with a free end is available to invade another duplex. If homologous DNA is present, RecA-dependent homologous recombination is promoted; if not (or if no autologous Chi site is present) the RecBCD/AddAB complex eventually degrades the DNA. We examined the distribution of recBCD and addAB genes among bacteria, and sought ways to distinguish them unambiguously. We examined bacterial species among 33 phyla, finding some unexpected distribution patterns. RecBCD and addAB are less conserved than recA, with the orthologous recB and addA genes more conserved than the recC or addB genes. We were able to classify RecB vs. AddA and RecC vs. AddB in some bacteria where this had not previously been done. We used logo analysis to identify sequence segments that are conserved, but differ between the RecBC and AddAB proteins, to help future differentiation between members of these two families.

Selection for Reducing Energy Cost of Protein Production Drives the GC Content and Amino Acid Composition Bias in Gene Transfer Agents.

Gene transfer agents (GTAs) are virus-like elements integrated into bacterial genomes, particularly, those of Alphaproteobacteria The GTAs can be induced under conditions of nutritional stress, incorporate random fragments of bacterial DNA into miniphage particles, lyse the host cells, and infect neighboring bacteria, thus enhancing horizontal gene transfer. We show that GTA genes evolve under conditions of pronounced positive selection for the reduction of the energy cost of protein production as shown by comparison of the amino acid compositions with those of both homologous viral genes and host genes. The energy saving in GTA genes is comparable to or even more pronounced than that in the genes encoding the most abundant, essential bacterial proteins. In cases in which viruses acquire genes from GTAs, the bias in amino acid composition disappears in the course of evolution, showing that reduction of the energy cost of protein production is an important factor of evolution of GTAs but not bacterial viruses. These findings strongly suggest that GTAs represent bacterial adaptations rather than selfish, virus-like elements. Because GTA production kills the host cell and does not propagate the GTA genome, it appears likely that the GTAs are retained in the course of evolution via kin or group selection. Therefore, we hypothesize that GTAs facilitate the survival of bacterial populations under energy-limiting conditions through the spread of metabolic and transport capabilities via horizontal gene transfer and increases in nutrient availability resulting from the altruistic suicide of GTA-producing cells.IMPORTANCE Kin selection and group selection remain controversial topics in evolutionary biology. We argue that these types of selection are likely to operate in bacterial populations by showing that bacterial gene transfer agents (GTAs), but not related viruses, evolve under conditions of positive selection for the reduction of the energy cost of GTA particle production. We hypothesize that GTAs are dedicated devices mediating the survival of bacteria under conditions of nutrient limitation. The benefits conferred by GTAs under nutritional stress conditions appear to include horizontal dissemination of genes that could provide bacteria with enhanced capabilities for nutrient utilization and increases of nutrient availability occurring through the lysis of GTA-producing bacteria.

Selfless viruses - the biology and regulation of gene transfer agents

Gene transfer agents (GTAs) are genetic elements that have the potential to carry out high frequency horizontal gene transfer. GTAs are similar to small bacteriophages in many ways but, instead of prioritizing the spread of their own genes, they package and disseminate the entire genome of their bacterial host. Indiscriminate transfer of bacterial genes could clearly have a major impact on bacterial evolution, fitness and antimicrobial resistance. Over the past decade, numerous pleiotropic systems have been shown to influence GTA production (e.g. nutrient stress, quorum sensing, SOS response etc.) but all act indirectly and so the mechanism of activation has remained elusive. I will present recent work that identified the missing link that couples GTA production to host regulatory pathways. I will also offer insights into the mechanism of random DNA packaging, the evolutionary role of GTAs in the environment and their potential ecological niche.

Phytoplankton pangenome reveals extensive prokaryotic horizontal gene transfer of diverse functions.

The extent and role of horizontal gene transfer (HGT) in phytoplankton and, more broadly, eukaryotic evolution remain controversial topics. Recent studies substantiate the importance of HGT in modifying or expanding functions such as metal or reactive species detoxification and buttressing halotolerance. Yet, the potential of HGT to significantly alter the fate of species in a major eukaryotic assemblage remains to be established. We provide such an example for the ecologically important lineages encompassed by cryptophytes, rhizarians, alveolates, stramenopiles, and haptophytes ("CRASH" taxa). We describe robust evidence of prokaryotic HGTs in these taxa affecting functions such as polysaccharide biosynthesis. Numbers of HGTs range from 0.16 to 1.44% of CRASH species gene inventories, comparable to the ca. 1% prokaryote-derived HGTs found in the genomes of extremophilic red algae. Our results substantially expand the impact of HGT in eukaryotes and define a set of general principles for prokaryotic gene fixation in phytoplankton genomes.

Mobile Genetic Elements and Natural Gene Transfer in Rumen Microbial Ecosystem

As technology is going be modern different changes that occur in the nature become studied. Rumen microbes especially rumen bacteria play a vital role in utilization of ruminants feed. Without rumen microbe’s rumen can’t function correctly. So, when we feed our animals, we are also feeding rumen microbes which convert the plant fiber to VFA which used by ruminants as an energy source for maintenance and production. Through the process these microbes change in their genetic structure and function because of natural gene transfer which is mediated by movable genetic elements like bacteriophage, plasmid, transposons and other segments. In this review prokaryotes which include bacteria and archae have got large cover than eukaryotes because most significant changes in rumen are carried by those organisms. HGT is the way to perform this function because it enables bacteria to respond and adapt to their environment much more rapidly by acquiring large DNA sequence from other bacterium in a single transfer and mechanisms of bacterial gene transfer include transformation, transduction and conjugation. So this event has an impact on the microbe themselves, for the rumen ecosystem, the animal and the environment where these changes are related. These changes include antibiotic resistance, better conversion of feeds and effects in methane and ammonia production. Keywords: Horizontal Gene Transfer, Prokaryotes, Rumen. Rumen Microbes DOI : 10.7176/ALST/78-03 Publication date: February 29 th 2020

Recombination and gene loss occur simultaneously during bacterial horizontal gene transfer.

Bacteria can acquire new genes by incorporating environmental DNA into their genomes, yet genome sizes stay relatively constant. In nature, gene acquisition is a rare event so it is difficult to observe. However, the Caulobacter crescentus CB2A genome contains 114 insertions of genetic material from the closely-related NA1000 strain, providing a unique opportunity to analyze the horizontal transfer of genetic material. Analyses of these insertions led to a new model that involves preferential recombination at non-homologous regions that are flanked by regions of homology and does not involve any mutational processes. The net result is the replacement of segments of the recipient genome instead of the simple addition of genetic material during horizontal gene transfer. Analyses of the genomes of closely related strains of other bacterial and archaea genera, suggested that horizontal gene transfer occurs preferentially in non-homologous regions in these organisms as well. Thus, it appears to be a general phenomenon that prokaryotic horizontal gene transfer occurs preferentially at sites where the incoming DNA contains a non-homologous region that is flanked by regions of homology. Therefore, gene replacement is a common phenomenon during horizontal gene transfer.