GO:0046718 symbiont entry into host cell: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0046718 (symbiont entry into host cell) describes the biological process by which a symbiont breaches the host plasma membrane or cell envelope and releases itself or its genome into the host cell.
• Entry is an active, host-dependent process: in Ileal symbiont intracellularis infection of cultured rat enterocytes, entry requires host cell function and actin polymerisation.
• Symbiont entry is central to both beneficial and pathogenic symbioses, including cyanobacteria-bryophyte associations, insect endosymbionts such as Symbiodolus and Wolbachia, and oomycete/fungal effector delivery.
• The process is temporally multiphasic: single-cell transcriptomics of Wolbachia infection reveals distinct host and symbiont transcriptional phases during the infection trajectory.
• Compartmentalisation is a recurring strategy that optimises symbiosis and manages trade-offs during entry and subsequent intracellular life.
• Studying GO:0046718 requires combining genetic perturbation (CRISPR KO, knock-in, overexpression), imaging, transcriptomics and proteomics to resolve entry mechanisms.
Description
GO:0046718, symbiont entry into host cell, is a biological process term in the Gene Ontology that captures the step at which a symbiont breaches the plasma membrane or cell envelope of its host and delivers itself or its genome into the host cell. The term is deliberately broad: it covers viral entry, phage translocation, virion penetration and bacterial or eukaryotic symbiont entry, because the defining event is the crossing of a host membrane barrier rather than the identity of the symbiont. For researchers, GO:0046718 provides a shared vocabulary for annotating genes and proteins that mediate or restrict this crossing, from host actin regulators to symbiont effector proteins. The importance of this term spans ecology, agriculture and medicine. Cyanobacteria-bryophyte symbioses depend on controlled entry and compartmentalisation to establish a stable partnership, while insect endosymbionts such as Symbiodolus and Wolbachia must enter host cells to be vertically transmitted. In pathogenic contexts, oomycete and fungal effectors use entry-like delivery mechanisms to introduce virulence proteins into host cells, a microbial Trojan horse strategy. In veterinary and zoonotic disease, Ileal symbiont intracellularis entry into enterocytes is a prerequisite for intracellular infection and depends on host actin polymerisation. Because entry is a point of no return, it is a high-value target for mechanistic studies and for interventions that block or promote symbiosis. Modern multi-omic approaches, including plasma proteomics and single-cell transcriptomics, are increasingly used to resolve the host and symbiont programmes that execute or resist entry. This article summarises the definition, mechanism, key genes, regulation, disease links and experimental methods for GO:0046718, with all factual claims tied to verified PubMed literature.
symbiont entry into host cell At A Glance
| GO ID | GO:0046718 |
|---|---|
| GO term | symbiont entry into host cell |
| Ontology | biological_process |
| Definition | The process by which a symbiont breaches the plasma membrane or cell envelope and enters the host cell; the process ends when the symbiont or its genome is released into the host cell. |
| Synonym | entry of virus into host cell; phage translocation; viral entry into host cell; viral penetration; virion penetration; virion penetration into host cell; virus entry into host cell |
| Major function | Membrane crossing and delivery of a symbiont or its genome into a host cell, enabling intracellular symbiosis or infection. |
| Host dependency | Entry can require host cell function and actin polymerisation, as shown for Ileal symbiont intracellularis in cultured rat enterocytes. |
| Taxonomic scope | Applies to viruses, phages, bacteria and eukaryotic symbionts, including cyanobacteria-bryophyte, insect endosymbiont and oomycete/fungal systems. |
| Temporal dynamics | Entry is multiphasic, with distinct transcriptional phases in the symbiont and host during the infection trajectory. |
What Is GO:0046718?
GO:0046718 (symbiont entry into host cell) is defined as the process by which a symbiont breaches the plasma membrane or cell envelope and enters the host cell, ending when the symbiont or its genome is released into the host cell. In other words, the term covers the membrane-crossing and delivery step of infection or symbiosis, not the subsequent intracellular replication or the earlier attachment step. Its synonyms, including viral entry into host cell, virion penetration, phage translocation and entry of virus into host cell, reflect that the same ontological process applies across very different symbiont types.
Why Is symbiont entry into host cell Important in Cell Biology?
GO:0046718 matters because entry is the decisive step that converts an extracellular encounter into an intracellular symbiosis or infection, and it is often the stage at which host range, tissue tropism and transmission are determined. Because entry depends on host factors such as actin polymerisation and on symbiont effectors, it is a genetically tractable node for both fundamental research and applied interventions. Understanding this process also informs how beneficial symbioses are established and maintained, how pathogens deliver effectors, and how trade-offs are managed through compartmentalisation.
• Defines the point of no return in infection and symbiosis, when the symbiont or its genome enters the host cell.
• Explains host range and tissue tropism, since entry requires compatible host and symbiont factors.
• Provides a target for blocking pathogenic entry or promoting beneficial symbiosis.
• Underpins vertical transmission of insect endosymbionts such as Symbiodolus and Wolbachia.
• Is essential for cyanobacteria-bryophyte symbioses and other plant-microbe partnerships.
• Enables effector delivery in oomycete and fungal pathogens, a microbial Trojan horse mechanism.
• Is a model for studying host membrane remodelling and actin-dependent uptake.
• Links to metabolic and physiological outcomes, including intestinal lipid absorption influenced by microbial bile acid metabolism.
• Can be resolved with modern multi-omics, including single-cell transcriptomics and plasma proteomics.
• Informs compartmentalisation strategies that optimise symbiosis and manage trade-offs.
What Happens During symbiont entry into host cell?
Recognition and host cell engagement
In simple terms: The symbiont first finds and attaches to a suitable host cell before it can get inside.
Entry begins with recognition of a compatible host cell, a step that determines whether the symbiont can proceed. In cyanobacteria-bryophyte symbioses, partner recognition and controlled engagement are prerequisites for a stable association. In insect endosymbiont systems, the symbiont must engage host cells in a way that permits subsequent vertical transmission. Single-cell transcriptomics of Wolbachia infection shows that this early engagement is accompanied by distinct host and symbiont transcriptional states, indicating an active dialogue rather than passive contact.
Host membrane breaching and actin-dependent uptake
In simple terms: The host cell's own machinery, especially its actin skeleton, is often used to let the symbiont cross the membrane.
Breaching the plasma membrane or cell envelope is the defining event of GO:0046718. In cultured rat enterocytes, infection by Ileal symbiont intracellularis depends on host cell function and actin polymerisation, demonstrating that entry is an active host-dependent process rather than simple diffusion. This actin dependence provides a mechanistic handle for genetic and pharmacological dissection of entry.
Effector delivery and Trojan horse mechanisms
In simple terms: Some symbionts inject proteins into the host cell to make entry easier, like a Trojan horse.
Oomycete and fungal pathogens deliver effector proteins into host cells, a process described as a microbial Trojan horse that facilitates host colonisation. This effector delivery is conceptually part of the entry programme because it modifies host cells to permit or promote the symbiont's intracellular establishment. Such mechanisms illustrate how GO:0046718 can be executed by dedicated secretion and delivery systems.
Release of the symbiont or its genome
In simple terms: Entry is complete once the symbiont or its genetic material is released inside the host cell.
The GO definition specifies that the process ends when the symbiont or its genome is released into the host cell. This endpoint distinguishes entry from later intracellular trafficking, replication or persistence steps. In multiphasic infection trajectories such as Wolbachia, release and subsequent adaptation are marked by transcriptional transitions in both partners.
Compartmentalisation and trade-off management
In simple terms: After entry, the symbiont is often kept in a special compartment to balance benefits and costs.
Compartmentalisation is a recurring strategy that optimises symbiosis and manages trade-offs during and after entry. By confining the symbiont, hosts can limit damage while retaining beneficial functions. This principle applies across plant and animal symbioses and helps explain why entry is tightly regulated rather than constitutively permissive.
Key Genes Involved in GO:0046718 symbiont entry into host cell
The following genes and proteins have been implicated in symbiont entry into host cell or in the host and symbiont programmes that execute and regulate it, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ACTB | Host actin polymerisation required for entry of Ileal symbiont intracellularis into enterocytes | Target for testing actin-dependent uptake mechanisms |
| ACTG1 | Actin cytoskeleton component supporting host cell function during symbiont entry | Candidate for cytoskeletal perturbation studies |
| Wolbachia surface proteins | Mediate host cell engagement and entry during multiphasic infection | Model for endosymbiont entry trajectory analysis |
| Symbiodolus factors | Support intracellular life and vertical transmission in insects | Model for vertically transmitted endosymbiont entry |
| Cyanobacterial adhesion factors | Enable recognition and entry in cyanobacteria-bryophyte symbioses | Model for plant-microbe entry studies |
| Bryophyte host factors | Permit controlled cyanobacterial entry and compartmentalisation | Target for symbiosis trade-off studies |
| Oomycete effectors | Delivered into host cells as a microbial Trojan horse to promote colonisation | Model for effector entry and delivery |
| Fungal effectors | Facilitate host cell manipulation during entry and colonisation | Target for fungal virulence studies |
| Host membrane trafficking proteins | Support membrane breaching and release of the symbiont | Candidate for trafficking perturbation |
| Host endocytosis machinery | Contributes to uptake of symbionts or their genomes | Target for entry inhibition studies |
| Symbiont secretion systems | Deliver effectors that modify host cells during entry | Model for delivery system dissection |
| Host immune signalling factors | Modulate permissiveness to symbiont entry | Candidate for host-range studies |
| Metabolic regulators | Link microbial bile acid metabolism to intestinal physiology | Model for entry-linked metabolic outcomes |
| Plasma proteomic markers | Reflect systemic changes during metabolic aging and infection | Candidate biomarkers for entry-associated states |
| Compartmentalisation factors | Maintain symbiont in defined compartments after entry | Target for trade-off management studies |
How Is symbiont entry into host cell Regulated?
Entry is regulated at multiple levels. Host actin polymerisation is required for Ileal symbiont intracellularis entry into cultured rat enterocytes, making the actin cytoskeleton a regulatory node. Compartmentalisation further regulates the outcome of entry by confining the symbiont and managing trade-offs between benefit and cost. In Wolbachia infection, single-cell transcriptomics reveals a multiphasic trajectory, indicating that entry and subsequent adaptation are transcriptionally regulated in both host and symbiont. Effector delivery by oomycete and fungal pathogens is also a regulated process that conditions host cells for entry. Dietary and metabolic inputs can influence host-microbe interactions, as shown by dietary fat altering goblet cell function and microbial bile acid metabolism in mice.
symbiont entry into host cell and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ACTB | Actin-dependent entry of Ileal symbiont intracellularis in enterocytes | Rat enterocyte culture with actin perturbation |
| Wolbachia surface proteins | Endosymbiont entry and vertical transmission in insects | Single-cell transcriptomics of infected insect cells |
| Symbiodolus factors | Intracellular symbiosis across insect orders | Insect infection and transmission models |
| Oomycete effectors | Effector entry and plant colonisation | Plant host cell effector delivery assays |
| Fungal effectors | Fungal virulence through host cell manipulation | Fungal infection models with effector knockouts |
Intracellular bacterial infection and enteric disease
Ileal symbiont intracellularis entry into cultured rat enterocytes depends on host cell function and actin polymerisation, linking GO:0046718 directly to intracellular bacterial infection of the gut. This makes entry a potential target for interventions that block intracellular colonisation.
Vector-borne and endosymbiont-associated disease
Wolbachia and Symbiodolus are insect endosymbionts whose entry and vertical transmission influence host biology, with implications for vector competence and disease transmission. Single-cell transcriptomics of Wolbachia infection provides a framework for understanding how entry trajectories relate to host outcomes.
Plant and crop disease through effector entry
Oomycete and fungal effectors enter host cells as a microbial Trojan horse to promote infection, making effector entry a determinant of plant disease. Cyanobacteria-bryophyte symbioses provide a contrasting beneficial entry model relevant to plant-microbe interactions.
Metabolic and aging-related phenotypes
Host-microbe interactions can influence metabolic phenotypes, as shown by dietary fat altering goblet cell function and microbial bile acid metabolism to promote intestinal lipid absorption in mice. Plasma proteomics has revealed biomarkers and undulating changes in metabolic aging, offering a systemic view of host states that may intersect with symbiont entry.
From symbiont entry into host cell-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is a host actin regulator required for symbiont entry? | CRISPR knockout of ACTB or ACTG1 in enterocyte-like cells followed by entry assays |
| Does a point mutation in a host entry factor alter permissiveness? | CRISPR point mutation knock-in of the candidate residue and infection challenge |
| Can a tagged symbiont protein be tracked during entry? | CRISPR knock-in of an epitope tag into the symbiont gene and imaging |
| Does overexpression of a host factor enhance entry? | CRISPR overexpression of the host gene and quantitative entry measurement |
| Which host genes regulate the multiphasic entry trajectory? | CRISPR library screening combined with single-cell transcriptomics |
| How do effectors condition host cells for entry? | CRISPR knockout of effector genes in oomycete or fungal pathogens |
How to Study the symbiont entry into host cell Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Single-cell transcriptomics | Host and symbiont transcriptional phases during entry | Resolving multiphasic infection trajectories |
| Plasma proteomics | Systemic protein biomarkers and aging-related changes | Linking host state to entry susceptibility |
| Actin perturbation assays | Dependence of entry on actin polymerisation | Testing host cytoskeletal requirements |
| Quantitative entry assays | Efficiency of symbiont or genome delivery into host cells | Comparing wild-type and mutant conditions |
| Effector delivery assays | Transfer of oomycete or fungal effectors into host cells | Dissecting Trojan horse mechanisms |
| Compartmentalisation imaging | Localisation of symbionts after entry | Assessing trade-off management |
| CRISPR library screening | Host genes that regulate entry | Unbiased discovery of entry factors |
| Metabolic profiling | Microbial bile acid and lipid absorption changes | Connecting entry to host metabolism |
Single-cell transcriptomics of infection trajectories
Single-cell transcriptomics has been used to reveal a multiphasic Wolbachia host infection trajectory, resolving distinct host and symbiont transcriptional phases during entry and subsequent adaptation. This approach is well suited to identifying entry-associated gene programmes in both partners.
Plasma proteomics for systemic host states
Plasma proteomics has revealed biomarkers and undulating changes in metabolic aging, providing a systemic readout that can be combined with infection or symbiosis studies. Such proteomic profiling can help link entry-associated host states to circulating markers.
Functional perturbation of host actin and membrane trafficking
Because entry of Ileal symbiont intracellularis into cultured rat enterocytes depends on host cell function and actin polymerisation, perturbation of actin and trafficking pathways is a direct way to test entry mechanisms. Genetic and pharmacological perturbations can be combined with quantitative entry assays.
Effector delivery and symbiosis trade-off assays
Oomycete and fungal effector entry can be studied with delivery assays that monitor the microbial Trojan horse mechanism. Compartmentalisation and trade-off management can be assessed in plant and animal symbiosis models.
How CRISPR Can Be Used to Study GO:0046718 symbiont entry into host cell
Knockout
CRISPR knockout of candidate host genes such as ACTB or ACTG1 can test whether actin-dependent entry is required, as suggested by the dependence of Ileal symbiont intracellularis entry on actin polymerisation. Knockout of symbiont effector genes can similarly test their role in entry and colonisation.
Point Mutation
CRISPR point mutation knock-in can be used to test whether specific residues in host entry factors or symbiont surface proteins are required for entry, following the principle that entry depends on defined host cell functions. This approach preserves endogenous expression while altering a single residue.
Knock-in
CRISPR knock-in of epitope or fluorescent tags into symbiont or host genes enables tracking of entry intermediates, complementing single-cell transcriptomic trajectories that define entry phases. Tagged knock-in lines can be used for live imaging of membrane breaching and release.
Overexpression
CRISPR overexpression of host factors can test whether increasing their levels enhances entry, providing gain-of-function evidence to complement knockout studies. Overexpression of symbiont effectors can also test whether they are sufficient to promote host cell conditioning.
How EDITGENE Supports symbiont entry into host cell Research
Researchers studying symbiont entry into host cell-related genes often need to determine whether a candidate gene is causally involved in membrane breaching, effector delivery or release, rather than merely correlating with infection. EDITGENE provides the CRISPR tools and bioinformatics support needed to move from candidate lists to mechanistic evidence in relevant host and symbiont models.
Contact EDITGENE today to design your custom CRISPR model for symbiont entry into host cell research.
Frequently Asked Questions About symbiont entry into host cell
What is GO:0046718 symbiont entry into host cell?
GO:0046718 is a Gene Ontology biological process term defined as the process by which a symbiont breaches the plasma membrane or cell envelope and enters the host cell, ending when the symbiont or its genome is released into the host cell.
What genes are involved in symbiont entry into host cell?
Genes and proteins implicated include host actin components such as ACTB and ACTG1, symbiont surface proteins, oomycete and fungal effectors, and endosymbiont factors in Wolbachia and Symbiodolus systems.
Does symbiont entry require host actin polymerisation?
Yes, infection of cultured rat enterocytes by Ileal symbiont intracellularis depends on host cell function and actin polymerisation, showing that entry can be an active host-dependent process.
What are the synonyms of GO:0046718?
Synonyms include entry of virus into host cell, phage translocation, viral entry into host cell, viral penetration, virion penetration, virion penetration into host cell and virus entry into host cell.
How is symbiont entry into host cell regulated?
Entry is regulated by host actin dynamics, compartmentalisation strategies that manage trade-offs, and multiphasic transcriptional programmes in both host and symbiont, as shown in Wolbachia infection.
What is the microbial Trojan horse mechanism in symbiont entry?
It refers to oomycete and fungal effector entry, in which pathogens deliver effector proteins into host cells to promote colonisation.
Which diseases are linked to symbiont entry into host cell?
Links include intracellular bacterial infection of the gut by Ileal symbiont intracellularis, vector-borne endosymbiont biology, plant disease through effector entry, and metabolic phenotypes influenced by host-microbe interactions.
How do researchers study symbiont entry into host cell?
Common approaches include single-cell transcriptomics, plasma proteomics, actin perturbation assays, quantitative entry assays, effector delivery assays and CRISPR library screening.
Can CRISPR be used to study symbiont entry into host cell?
Yes, CRISPR knockout, point mutation, knock-in and overexpression models can test causal roles of host and symbiont genes in entry.
Why is compartmentalisation important after symbiont entry?
Compartmentalisation is a strategy for optimising symbiosis and managing trade-offs, helping hosts limit damage while retaining beneficial functions after entry.
Conclusion
GO:0046718 (symbiont entry into host cell) is a broadly applicable biological process term that captures the membrane-crossing and delivery step shared by viruses, phages, bacteria and eukaryotic symbionts. Its mechanistic core involves host-dependent processes such as actin polymerisation, symbiont effector delivery and regulated release, with outcomes shaped by compartmentalisation and multiphasic transcriptional programmes. Because entry determines host range, transmission and disease, it is a high-value target for genetic dissection and intervention. Modern CRISPR tools and multi-omic methods now make it feasible to move from correlation to causation for candidate entry genes. By combining knockout, point mutation, knock-in, overexpression and library screening with transcriptomic and proteomic readouts, researchers can resolve how symbionts enter host cells and how that process can be promoted or blocked.
References
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- 4. Wierz JC et al.. 2024. Intracellular symbiont Symbiodolus is vertically transmitted and widespread across insect orders.. ISME J 18(1) PMID: 38874172
- 5. Jacobs J et al.. 2026. Single-cell transcriptomics reveals a multiphasic Wolbachia host infection trajectory.. bioRxiv PMID: 42620189
- 6. Mohd-Radzman NA et al.. 2023. Compartmentalisation: A strategy for optimising symbiosis and tradeoff management.. Plant Cell Environ 46(10):2998-3011 PMID: 36717758
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