-
Frontiers in Cellular and Infection... 2023Extracellular vesicles (EVs or exosomes) are well described for bacterial pathogens associated with our gastrointestinal system, and more recently as a novel mechanism... (Review)
Review
Extracellular vesicles (EVs or exosomes) are well described for bacterial pathogens associated with our gastrointestinal system, and more recently as a novel mechanism for environmental persistence, dissemination and infection for human enteric viruses. However, the roles played by EVs in the ancient arms race that continues between amoebae and one of their prey, , is poorly understood. At best we know of intracellular vesicles of amoebae containing a mix of bacterial prey species, which also provides an enhanced niche for bacteriophage infection/spread. Free-living amoeba-associated pathogens have recently been recognized to have enhanced resistance to disinfection and environmental stressors, adding to previously understood (but for relatively few species of) bacteria sequestered within amoebal cysts. However, the focus of the current work is to review the likely impacts of large numbers of respiratory-sized EVs containing numerous cells studied in pure and biofilm systems with mixed prey species. These encapsulated pathogens are orders of magnitude more resistant to disinfection than free cells, and our engineered systems with residual disinfectants could promote evolution of resistance (including AMR), enhanced virulence and EV release. All these are key features for evolution within a dead-end human pathogen post lung infection. Traditional single-hit pathogen infection models used to estimate the probability of infection/disease and critical environmental concentrations quantitative microbial risk assessments may also need to change. In short, recognizing that EV-packaged cells are highly virulent units for transmission of legionellae, which may also modulate/avoid human host immune responses. Key data gaps are raised and a previous conceptual model expanded upon to clarify where biofilm EVs could play a role promoting risk as well as inform a more wholistic management program to proactively control legionellosis.
Topics: Humans; Legionella; Water; Amoeba; Legionella pneumophila; Sepsis; Extracellular Vesicles
PubMed: 37274310
DOI: 10.3389/fcimb.2023.1200478 -
Molecular Medicine Reports Jun 2022The Mimivirus is a giant virus that infects amoebae and was long considered to be a bacterium due to its size. The viral particles are composed of a protein capsid of... (Review)
Review
The Mimivirus is a giant virus that infects amoebae and was long considered to be a bacterium due to its size. The viral particles are composed of a protein capsid of ~500 nm in diameter, which is enclosed in a polysaccharide layer in which ~120‑140 nm long fibers are embedded, resulting in an overall diameter of 700 nm. The virus has a genome size of 1.2 Mb DNA, and surprisingly, replicates only in the cytoplasm of the infected cells without entering the nucleus, which is a unique characteristic among DNA viruses. Their existence is undeniable; however, as with any novel discovery, there is still uncertainty concerning their pathogenicity mechanisms in humans and the nature of the Mimivirus virophage resistance element system (MIMIVIRE), a term given to describe the immune network of the Mimivirus, which closely resembles the CRISPR‑Cas system. The scope of the present review is to discuss the recent developments derived from structural and functional studies performed on the distinctive characteristics of the Mimivirus, and from studies concerning their putative clinical relevance in humans.
Topics: Amoeba; CRISPR-Cas Systems; Capsid; Giant Viruses; Humans; Mimiviridae
PubMed: 35506451
DOI: 10.3892/mmr.2022.12723 -
FEMS Microbiology Ecology Dec 2020Naegleria fowleri is a free-living protozoan that resides in soil and freshwater. Human intranasal amoebae exposure through water or potentially dust particles can... (Review)
Review
Naegleria fowleri is a free-living protozoan that resides in soil and freshwater. Human intranasal amoebae exposure through water or potentially dust particles can culminate in primary amoebic meningoencephalitis, which generally causes death. While many questions remain regarding pathogenesis, the microbial ecology of N. fowleri is even less understood. This review outlines current knowledge of the environmental abiotic and biotic factors that affect the distribution and abundance of N. fowleri. Although the impacts of some abiotic factors remain poorly investigated or inconclusive, N. fowleri appears to have a wide pH range, low salinity tolerance and thermophilic preference. From what is known about biotic factors, the amoebae preferentially feed upon bacteria and are preyed upon by other free-living amoebae. Additional laboratory and environmental studies are needed to fill in knowledge gaps, which are crucial for surveillance and management of N. fowleri in freshwaters. As surface water temperatures increase with climate change, it is likely that this amoeba will pose a greater threat to human health, suggesting that identifying its abiotic and biotic preferences is critical to mitigating this risk.
Topics: Amoeba; Central Nervous System Protozoal Infections; Fresh Water; Humans; Naegleria fowleri; Water
PubMed: 33242082
DOI: 10.1093/femsec/fiaa238 -
Developmental Dynamics : An Official... Mar 2023Animal regeneration is a fascinating field of research that has captured the attention of many generations of scientists. Among the cellular mechanisms underlying tissue... (Review)
Review
Animal regeneration is a fascinating field of research that has captured the attention of many generations of scientists. Among the cellular mechanisms underlying tissue and organ regeneration, we highlight the role of phagocytic ameboid cells (PACs). Beyond their ability to engulf nutritional particles, microbes, and apoptotic cells, their involvement in regeneration has been widely documented. It has been extensively described that, at least in part, animal regenerative mechanisms rely on PACs that serve as a hub for a range of critical physiological functions, both in health and disease. Considering the phylogenetics of PAC evolution, and the loss and gain of nutritional, immunological, and regenerative potential across Metazoa, we aim to discuss when and how phagocytic activity was first co-opted to regenerative tissue repair. We propose that the gradual specialization of PACs during metazoan derivation may have contributed to the loss of regenerative potential in animals, with critical impacts on potential translational strategies for regenerative medicine.
Topics: Animals; Amoeba; Regeneration; Wound Healing; Phylogeny; Regenerative Medicine
PubMed: 36205096
DOI: 10.1002/dvdy.543 -
International Journal For Parasitology.... Dec 2021The Free-Living Amoeba species, Naegleria fowleri is the causative agent of a lethal encephalitis known as Primary Amoebic Encephalitis (PAM). Moreover, most of the...
The Free-Living Amoeba species, Naegleria fowleri is the causative agent of a lethal encephalitis known as Primary Amoebic Encephalitis (PAM). Moreover, most of the reported cases are often related to swimming and/or diving in aquatic environments. In addition, the current therapeutic options against PAM are not fully effective and hence, there is an urgent need to develop novel therapeutic agents against this disease. Previously isobenzofuranones compounds have been reported to present antiprotozoal and antifungal activity among others. However, to the best of our knowledge, these molecules have not been previously tested against N. fowleri. Therefore, the aim of this study was to evaluate the activity of 14 novel isobenzofuranones against this pathogenic amoeba. The most active and less toxic molecules, were assayed in order to check induction of Programmed Cell Death (PCD) in the treated amoebae. The obtained results showed that these molecules were able to eliminate N. fowleri trophozoites and also induced PCD. Therefore, the tested isobenzofuranones could be potential therapeutic candidates for the treatment of PAM.
Topics: Amebiasis; Amoeba; Animals; Antiprotozoal Agents; Naegleria fowleri; Trophozoites
PubMed: 34627024
DOI: 10.1016/j.ijpddr.2021.09.004 -
PLoS Neglected Tropical Diseases Jul 2016Free-living amoebae are present worldwide. They can survive in different environment causing human diseases in some instances. Acanthamoeba sp. is known for causing...
BACKGROUND
Free-living amoebae are present worldwide. They can survive in different environment causing human diseases in some instances. Acanthamoeba sp. is known for causing sight-threatening keratitis in humans. Free-living amoeba keratitis is more common in developing countries. Amoebae of family Vahlkampfiidae are rarely reported to cause such affections. A new genus, Allovahlkampfia spelaea was recently identified from caves with no data about pathogenicity in humans. We tried to identify the causative free-living amoeba in a case of keratitis in an Egyptian patient using morphological and molecular techniques.
METHODS
Pathogenic amoebae were culture using monoxenic culture system. Identification through morphological features and 18S ribosomal RNA subunit DNA amplification and sequencing was done. Pathogenicity to laboratory rabbits and ability to produce keratitis were assessed experimentally.
RESULTS
Allovahlkampfia spelaea was identified as a cause of human keratitis. Whole sequence of 18S ribosomal subunit DNA was sequenced and assembled. The Egyptian strain was closely related to SK1 strain isolated in Slovenia. The ability to induce keratitis was confirmed using animal model.
CONCLUSIONS
This the first time to report Allovahlkampfia spelaea as a human pathogen. Combining both molecular and morphological identification is critical to correctly diagnose amoebae causing keratitis in humans. Use of different pairs of primers and sequencing amplified DNA is needed to prevent misdiagnosis.
Topics: Acanthamoeba; Amebiasis; Animals; DNA, Protozoan; DNA, Ribosomal; Disease Models, Animal; Humans; Keratitis; Phylogeny; RNA, Ribosomal, 18S; Rabbits
PubMed: 27415799
DOI: 10.1371/journal.pntd.0004841 -
Journal of Veterinary Diagnostic... May 2023Free-living amoebae are rare causes of morbidity and mortality in humans and animals around the globe. Because the route of exposure and clinical progression of disease... (Review)
Review
Free-living amoebae are rare causes of morbidity and mortality in humans and animals around the globe. Because the route of exposure and clinical progression of disease caused by different species of amoebae may vary in people and animals, determining the species of amoeba present is important. We describe here a fatal infection by the free-living amoeba in a Siberian tiger (). The 17-y-old patient had a rapid clinical decline after a peracute onset of severe lethargy, dull mentation, and anorexia. Autopsy did not identify a cause of death. Histology revealed inflammation associated with amoebic trophozoites in the brain, lungs, and iris of one eye. These amoebae were confirmed to be based on a PCR assay and sequencing. Although there are subtle morphologic differences between cyst stages of spp., , and when present and identified on routine staining, other modalities, including PCR, immunofluorescence, electron microscopy, and immunohistochemistry, are typically utilized to confirm the pathogen involved in these cases. We review the reports of balamuthosis in animals.
Topics: Humans; Animals; Tigers; Amebiasis; Amoeba; Acanthamoeba; Naegleria fowleri; Balamuthia mandrillaris
PubMed: 36908206
DOI: 10.1177/10406387231160771 -
Anais Da Academia Brasileira de Ciencias 2023Within each ecosystem, organisms and populations maintain a complex set of relationships. These interactions can determine the distribution area of a species and play an...
Within each ecosystem, organisms and populations maintain a complex set of relationships. These interactions can determine the distribution area of a species and play an essential role in its evolution. Parasites are ubiquitous components of nature and have a high influence on various aspects of the biology and ecology of organisms, affecting the populations of their hosts and, therefore, their communities and ecosystems. Free-living amoebae are unicellular organisms that can be found in water, soil or air. Some species are of great importance in human health. In Hydra, there are several reports of Hydramoeba hydroxena infections. In this work we present a double parasitosis: two concatenated infectious periods in the host polyp of Hydra vulgaris and Hydra vulgaris pedunculata for three freshwater bodies in the province of Buenos Aires, Argentina. Hydramoeba sp. and Acanthoamoeba sp. unchain a series of anatomical lesions that in all cases cause the death of the polyps due to total disintegration. This finding becomes important at a sanitary level due to the appearance of Acanthoamoeba sp. in waters associated with human recreational activities; For the Hydra genus, the importance lies at an ecological and evolutionary level, considering the possible impact on its natural populations.
Topics: Humans; Animals; Amoeba; Ecosystem; Hydra; Acanthamoeba; Argentina
PubMed: 37162082
DOI: 10.1590/0001-3765202320211025 -
MSystems Oct 2022The social amoeba Dictyostelium discoideum is a predatory soil protist frequently used for studying host-pathogen interactions. A subset of D. discoideum strains...
The social amoeba Dictyostelium discoideum is a predatory soil protist frequently used for studying host-pathogen interactions. A subset of D. discoideum strains isolated from soil persistently carry symbiotic , recently formally described as , , and . The three facultative symbiont species of D. discoideum present a unique opportunity to study a naturally occurring symbiosis in a laboratory model protist. There is a large difference in genome size between (8.7 million base pairs [Mbp]) versus and (4.1 Mbp). We took a comparative genomics approach and compared the three genomes of D. discoideum symbionts to 12 additional genomes to test for genome evolution patterns that frequently accompany host adaptation. Overall, is difficult to distinguish from other based on its genome size and content, but the reduced genomes of and display characteristics indicative of genome streamlining rather than deterioration during adaptation to their protist hosts. In addition, D. discoideum-symbiont genomes have increased secretion system and motility genes that may mediate interactions with their host. Specifically, adjacent BurBor-like type 3 and T6SS-5-like type 6 secretion system operons shared among all three D. discoideum-symbiont genomes may be important for host interaction. Horizontal transfer of these secretion system operons within the amoeba host environment may have contributed to the unique ability of these symbionts to establish and maintain a symbiotic relationship with D. discoideum. Protists are a diverse group of typically single cell eukaryotes. Bacteria and archaea that form long-term symbiotic relationships with protists may evolve in additional ways than those in relationships with multicellular eukaryotes such as plants, animals, or fungi. Social amoebas are a predatory soil protist sometimes found with symbiotic bacteria living inside their cells. They present a unique opportunity to explore a naturally occurring symbiosis in a protist frequently used for studying host-pathogen interactions. We show that one amoeba-symbiont species is similar to other related bacteria in genome size and content, while the two reduced-genome-symbiont species show characteristics of genome streamlining rather than deterioration during adaptation to their host. We also identify sets of genes present in all three amoeba-symbiont genomes that are potentially used for host-symbiont interactions. Because the amoeba symbionts are distantly related, the amoeba host environment may be where these genes were shared among symbionts.
Topics: Animals; Amoeba; Dictyostelium; Eukaryota; Burkholderiaceae; Bacteria; Soil
PubMed: 36098425
DOI: 10.1128/msystems.00562-22 -
Frontiers in Cellular and Infection... 2018A small subset of bacteria in soil interact directly with eukaryotes. Which ones do so can reveal what is important to a eukaryote and how eukaryote defenses might be...
A small subset of bacteria in soil interact directly with eukaryotes. Which ones do so can reveal what is important to a eukaryote and how eukaryote defenses might be breached. Soil amoebae are simple eukaryotic organisms and as such could be particularly good for understanding how eukaryote microbiomes originate and are maintained. One such amoeba, , has both permanent and temporary associations with bacteria. Here we focus on culturable bacterial associates in order to interrogate their relationship with . To do this, we isolated over 250 fruiting body samples from soil and deer feces at Mountain Lake Biological Station. In one-third of the wild we tested, one to six bacterial species were found per fruiting body sorus (spore mass) for a total of 174 bacterial isolates. The remaining two-thirds of fruiting body samples did not contain culturable bacteria, as is thought to be the norm. A majority (71.4%) of the unique bacterial haplotypes are in Proteobacteria. The rest are in either Actinobacteria, Bacteriodetes, or Firmicutes. The highest bacterial diversity was found in fruiting bodies originating from deer feces (27 OTUs), greater than either of those originating in shallow (11 OTUs) or in deep soil (4 OTUs). Rarefaction curves and the Chao1 estimator for species richness indicated the diversity in any substrate was not fully sampled, but for soil it came close. A majority of the -associated bacteria were edible by and supported its growth (75.2% for feces and 81.8% for soil habitats). However, we found several bacteria genera were able to evade phagocytosis and persist in cells through one or more social cycles. This study focuses not on the entire microbiome, but on the culturable subset of bacteria that have important eukaryote interactions as prey, symbionts, or pathogens. These eukaryote and bacteria interactions may provide fertile ground for investigations of bacteria using amoebas to gain an initial foothold in eukaryotes and of the origins of symbiosis and simple microbiomes.
Topics: Amoeba; Animals; Bacteria; Biodiversity; Deer; Dictyostelium; Feces; Microbiota; Phagocytosis; Phylogeny; Soil; Soil Microbiology; Symbiosis; Virginia
PubMed: 30533398
DOI: 10.3389/fcimb.2018.00411