Intermicrobial Hitchhiking: How Nonmotile Microbes Leverage Communal Motility
2020; Elsevier BV; Volume: 29; Issue: 6 Linguagem: Inglês
10.1016/j.tim.2020.10.005
ISSN1878-4380
AutoresAlise R. Muok, Ariane Briegel,
Tópico(s)Legionella and Acanthamoeba research
ResumoSporadic reports demonstrate that some nonmotile microbes utilize trans-species hitchhiking to traverse their environment.Hitchhiking has been observed with eukaryotic and prokaryotic microbes.Four general hitchhiking mechanisms have been elucidated thus far: mechanical pushing by motile cells, direct attachment to cell bodies, direct attachment to bacterial flagella, and internal transport by cells.Several immotile human and plant pathogens hitchhike motile microbes that are natively found in their vicinity.In some instances, hitchhiking is implicated in infectivity mechanisms of microbial pathogens. Motility allows many microbes to traverse their environment to find nutrient sources or escape unfavorable environments. However, some microbes are nonmotile and are restricted to their immediate conditions. Intriguingly, sporadic reports have demonstrated that many nonmotile microbes can utilize the motility machinery of other microbes in their vicinity. This form of transportation, called hitchhiking, has been observed with both prokaryotic and eukaryotic microbes. Importantly, many hitchhiking microbes are pathogenic to humans or plants. Here, we discuss reports of intermicrobial hitchhiking to generate a comprehensive view of hitchhiking mechanisms and how such interactions may influence human and plant health. We hypothesize that microbial hitchhiking is ubiquitous in nature and may become the subject of an independent subfield of research in microbiology. Motility allows many microbes to traverse their environment to find nutrient sources or escape unfavorable environments. However, some microbes are nonmotile and are restricted to their immediate conditions. Intriguingly, sporadic reports have demonstrated that many nonmotile microbes can utilize the motility machinery of other microbes in their vicinity. This form of transportation, called hitchhiking, has been observed with both prokaryotic and eukaryotic microbes. Importantly, many hitchhiking microbes are pathogenic to humans or plants. Here, we discuss reports of intermicrobial hitchhiking to generate a comprehensive view of hitchhiking mechanisms and how such interactions may influence human and plant health. We hypothesize that microbial hitchhiking is ubiquitous in nature and may become the subject of an independent subfield of research in microbiology. Motility Behaviors of Motile and Nonmotile MicrobesCell motility is responsible for a variety of complex and fascinating behaviors that are crucial for survival. Many free-living motile microbes utilize motility machinery to traverse their environment to find optimal conditions. For microbial pathogens, this same process is often utilized to invade host tissues [1.Matilla M.A. Krell T. The effect of bacterial chemotaxis on host infection and pathogenicity.FEMS Microbiol. Rev. 2018; 42: 40-67Crossref Scopus (122) Google Scholar,2.Sze C.W. et al.Borrelia burgdorferi needs chemotaxis to establish infection in mammals and to accomplish its enzootic cycle.Infect. Immun. 2012; 80: 2485-2492Crossref PubMed Scopus (47) Google Scholar]. To combat such invading microbes, some types of immune cells also employ motility to chase and destroy these pathogens [3.Jones G.E. Cellular signaling in macrophage migration and chemotaxis.J. Leukoc. Biol. 2000; 68: 593-602PubMed Google Scholar,4.Petri B. Sanz M.J. Neutrophil chemotaxis.Cell Tissue Res. 2018; 371: 425-436Crossref PubMed Scopus (92) Google Scholar]. Cells utilize different machineries for motility depending on the specific organism and environment. In liquid environments, cells can propel themselves through swimming (see Glossary) motility via rotating or beating extracellular filamentous appendages called flagella and cilia [5.Cappuccinelli P. The movement of eukaryotic cells.in: Motility of Living Cells. Springer, Dordrecht1980: 59-74Crossref Google Scholar,6.Jarrell K.F. McBride M.J. The surprisingly diverse ways that prokaryotes move.Nat. Rev. Microbiol. 2008; 6: 466-476Crossref PubMed Scopus (375) Google Scholar]. On surfaces, cells can move by utilizing other motile behaviors such as crawling, gliding, sliding, swarming, or twitching [5.Cappuccinelli P. The movement of eukaryotic cells.in: Motility of Living Cells. Springer, Dordrecht1980: 59-74Crossref Google Scholar,6.Jarrell K.F. McBride M.J. The surprisingly diverse ways that prokaryotes move.Nat. Rev. Microbiol. 2008; 6: 466-476Crossref PubMed Scopus (375) Google Scholar]. Many of these behaviors depend on a process called chemotaxis which allows the cell to sense its chemical environment and control its movement toward favorable molecules such as nutrients or away from deleterious compounds [2.Sze C.W. et al.Borrelia burgdorferi needs chemotaxis to establish infection in mammals and to accomplish its enzootic cycle.Infect. Immun. 2012; 80: 2485-2492Crossref PubMed Scopus (47) Google Scholar, 3.Jones G.E. Cellular signaling in macrophage migration and chemotaxis.J. Leukoc. Biol. 2000; 68: 593-602PubMed Google Scholar, 4.Petri B. Sanz M.J. Neutrophil chemotaxis.Cell Tissue Res. 2018; 371: 425-436Crossref PubMed Scopus (92) Google Scholar,7.Wadhams G.H. Armitage J.P. Making sense of it all: Bacterial chemotaxis.Nat. Rev. Mol. Cell Biol. 2004; 5: 1024-1037Crossref PubMed Scopus (934) Google Scholar].Although these forms of motility are present in diverse organisms, some microbes are nonmotile and lack any such machinery or are nonmotile under certain conditions. However, emerging research has identified a unique form of dispersal used by many microbes – hitchhiking on motile microbes. Hitchhiking allows otherwise nonmotile microbes to traverse their environment by effectively using the motility machinery of the motile partner. Remarkably, hitchhiking behavior has been revealed in both prokaryotic and eukaryotic microbes, and four general mechanisms have been elucidated: mechanical pushing by motile cells, direct attachment to cell bodies, direct attachment to bacterial flagella, and internal transport by cells. Here, we discuss reports of intermicrobial hitchhiking mechanisms that occur across taxonomic kingdoms and consider their potential impacts on human and plant health. However, it should be noted that microbes can also be transported by small animals [8.Becher P.G. et al.Developmentally regulated volatiles geosmin and 2-methylisoborneol attract a soil arthropod to Streptomyces bacteria promoting spore dispersal.Nat. Microbiol. 2020; 5: 821-829Crossref PubMed Scopus (53) Google Scholar, 9.Kim D.R. et al.A mutualistic interaction between Streptomyces bacteria, strawberry plants and pollinating bees.Nat. 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Additionally, phage particles can be transported by motile bacteria, but those findings [16.Ping D. et al.Hitchhiking, collapse, and contingency in phage infections of migrating bacterial populations.ISME J. 2020; 14: 2007-2018Crossref PubMed Scopus (7) Google Scholar] will not be discussed here.Reports of Microbial HitchhikingHitchhiking among BacteriaTransport via hitchhiking occurs among bacteria found in the soil [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar, 18.Inghama C.J. et al.Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.Proc. Natl. Acad. Sci. U. S. A. 2011; 108: 19731-19736Crossref PubMed Scopus (65) Google Scholar, 19.Muok A.R. et al.Microbial piggy-back: how Streptomyces spores are transported by motile soil bacteria.bioRxiv. 2020; (Published online June 18, 2020. 10.1101/2020.06.18.158626)Google Scholar], on plant tissues [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar, 18.Inghama C.J. et al.Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.Proc. Natl. Acad. Sci. U. S. A. 2011; 108: 19731-19736Crossref PubMed Scopus (65) Google Scholar, 19.Muok A.R. et al.Microbial piggy-back: how Streptomyces spores are transported by motile soil bacteria.bioRxiv. 2020; (Published online June 18, 2020. 10.1101/2020.06.18.158626)Google Scholar], on abiotic surfaces [18.Inghama C.J. et al.Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.Proc. Natl. Acad. Sci. U. S. A. 2011; 108: 19731-19736Crossref PubMed Scopus (65) Google Scholar,20.Samad T. et al.Swimming bacteria promote dispersal of non-motile staphylococcal species.ISME J. 2017; 11: 1933-1937Crossref PubMed Scopus (22) Google Scholar], and in human tissues [20.Samad T. et al.Swimming bacteria promote dispersal of non-motile staphylococcal species.ISME J. 2017; 11: 1933-1937Crossref PubMed Scopus (22) Google Scholar, 21.Rowbotham T.J. Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae.J. Clin. Pathol. 1980; 33: 1179-1183Crossref PubMed Scopus (712) Google Scholar, 22.Shrivastava A. et al.Cargo transport shapes the spatial organization of a microbial community.Proc. Natl. Acad. Sci. U. S. A. 2018; 115: 8633-8638Crossref PubMed Scopus (27) Google Scholar]. Hitchhiking is advantageous to nonmotile microbes that would otherwise occupy a single location and can also be favorable to the motile partner. For example, the soil-dwelling motile bacterium Paenibacillus vortex is noted for its 'hyper-swarming' behavior. P. vortex can swarm on hard surfaces, whereas most other bacteria are nonmotile under such conditions. To aid in its migration, P. vortex is able to carry antibiotic-resistant nonmotile bacterial 'cargo' at the leading edge of the swarm (Figure 1A , Key Figure) [23.Finkelshtein A. et al.Bacterial swarms recruit cargo bacteria to pave the way in toxic environments.mBio. 2015; 6: 1-10Crossref Scopus (48) Google Scholar]. As the cargo degrades antibiotics to nonlethal substances, the trailing P. vortex swarm can then occupy the previously toxic niche. P. vortex can effectively carry many nonmotile bacteria as cargo (nonmotile strains of Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes) and this cotransport can be advantageous as long as the cargo possesses the antibiotic resistance necessary for survival in the new niche [23.Finkelshtein A. et al.Bacterial swarms recruit cargo bacteria to pave the way in toxic environments.mBio. 2015; 6: 1-10Crossref Scopus (48) Google Scholar].It is still unclear how the cargo is transported by P. vortex. While there is some indication that the cargo may interact with P. vortex flagella, the cargo may also be mechanically pushed by the P. vortex at the leading edge of the swarm. Indeed, a recent study has found that, in the presence of crawling Acinetobacter baylyi, hitchhiking E. coli cells are always found at the leading edge of the growing A. baylyi colony [24.Xiong L. et al.Flower-like patterns in multi-species bacterial colonies.eLife. 2020; 9: 1-27Crossref Scopus (19) Google Scholar]. The presence of E. coli at the colony boundary creates instabilities in the region that ultimately result in the formation of macroscopically visible flower-like patterns of the E. coli cells. Comigration experiments and computational modeling of these patterns suggest that E. coli is kept at the leading edge by pushing and bumping forces generated by the A. baylyi cells (Figure 1A) [24.Xiong L. et al.Flower-like patterns in multi-species bacterial colonies.eLife. 2020; 9: 1-27Crossref Scopus (19) Google Scholar]. Nevertheless, the presence of similar migration patterns among these diverse bacteria suggests that hitchhiking bacterial migration at the colony leading edge may be a common occurrence in nature.In addition to carrying antibiotic-resistant cargo, P. vortex can also carry the phytopathogenic bacterium Xanthomonas perforans [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar]. Unlike P. vortex, X. perforans is nonmotile on hard surfaces. Remarkably, X. perforans is able to attract leaf-dwelling P. vortex to its immediate location on the leaves through the secretion of airborne volatile compounds. The P. vortex then disperses X. perforans across the leaf, potentially helping it to infect plant tissues [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar]. Scanning electron microscopy images show that swarming P. vortex cells form multilayered 'rafts' and that the X. perforans cells are localized on top of these rafts, indicating that the nonmotile cells may 'surf' on them for dispersal (Figure 1B) [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar]. However, it is unclear if the X. perforans cells preferentially attach to a specific location or feature on the P. vortex cells, such as flagella or the cell wall.P. vortex is not the only bacterium that serves as a raft for riding hitchhikers. In a similar fashion, Capnocytophaga gingivalis, which is an opportunistic pathogen found in the human oral microbiome, can disperse several nonmotile bacteria commonly associated with periodontal diseases [22.Shrivastava A. et al.Cargo transport shapes the spatial organization of a microbial community.Proc. Natl. Acad. Sci. U. S. A. 2018; 115: 8633-8638Crossref PubMed Scopus (27) Google Scholar]. C. gingivalis forms multilayered colonies that glide on top of one another. Microscopic examination of living bacterial communities demonstrates that several species of nonmotile bacteria (Porphyromonas endodontalis, Prevotella oris, Parvimonas micra, Actinomyces sp. Taxon-169, Fusobacterium nucleatum, Streptococcus sanguinis, and Veillonella parvula) attach directly to the C. gingivalis cell body and continuously circulate from one cell pole to the other during transport (Figure 1C) [22.Shrivastava A. et al.Cargo transport shapes the spatial organization of a microbial community.Proc. Natl. Acad. Sci. U. S. A. 2018; 115: 8633-8638Crossref PubMed Scopus (27) Google Scholar]. The observed attachment and circulation pattern are due to the presence of polysaccharide-binding protein, SprB, on the C. gingivalis cell surface. This protein interacts with the cell wall of the hitchhiking bacteria. Collectively, these interactions allow substantial transport of the hitchhikers and facilitate specific spatial organizations of the microbial communities that establish over time [22.Shrivastava A. et al.Cargo transport shapes the spatial organization of a microbial community.Proc. Natl. Acad. Sci. U. S. A. 2018; 115: 8633-8638Crossref PubMed Scopus (27) Google Scholar].Hitchhiking by nonmotile opportunistic pathogens has also been reported in some staphylococcal species (Staphylococcus aureus and Staphylococcus epidermidis) [20.Samad T. et al.Swimming bacteria promote dispersal of non-motile staphylococcal species.ISME J. 2017; 11: 1933-1937Crossref PubMed Scopus (22) Google Scholar]. These bacteria are able to adhere directly to the cell bodies of swimming bacteria (Pseudomonas aeruginosa and Escherichia coli) for transport and are subsequently associated with biofilms made by their mobile partners (Figure 1D) [20.Samad T. et al.Swimming bacteria promote dispersal of non-motile staphylococcal species.ISME J. 2017; 11: 1933-1937Crossref PubMed Scopus (22) Google Scholar]. This interaction allows S. aureus and S. epidermidis to colonize niches that are otherwise inaccessible to them.In the studies discussed thus far, the hitchhikers were metabolically active bacteria. However, nonmotile bacterial spores from streptomycetes are also capable of hitchhiking on motile bacteria [19.Muok A.R. et al.Microbial piggy-back: how Streptomyces spores are transported by motile soil bacteria.bioRxiv. 2020; (Published online June 18, 2020. 10.1101/2020.06.18.158626)Google Scholar]. Spores from several Streptomyces species (Streptomyces coelicolor, Streptomyces tendae, Streptomyces griseus, and Streptomyces scabies) are able to attach directly to the flagella of swarming soil bacteria (Bacillus subtilis and Pseudomonas fluorescens) and are translocated to plant tissues where they can germinate (Figure 1E). Dispersal can occur over long distances (at least 10 cm). The interaction between flagella and spores is facilitated by two spore coat proteins, RdlA and RdlB, that compose the spore coat rodlet layer [19.Muok A.R. et al.Microbial piggy-back: how Streptomyces spores are transported by motile soil bacteria.bioRxiv. 2020; (Published online June 18, 2020. 10.1101/2020.06.18.158626)Google Scholar,25.Claessen D. et al.The formation of the rodlet layer of streptomycetes is the result of the interplay between rodlins and chaplins.Mol. Microbiol. 2004; 53: 433-443Crossref PubMed Scopus (109) Google Scholar].Comigration of Bacteria and FungiAnalogous to the transportation of Streptomyces spores, the nonmotile conidia (fungal spores) from some Aspergillus and Penicillium species also hitchhike on swarming soil-dwelling bacteria via direct attachment to flagella (Figure 1E) [18.Inghama C.J. et al.Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.Proc. Natl. Acad. Sci. U. S. A. 2011; 108: 19731-19736Crossref PubMed Scopus (65) Google Scholar]. While several motile bacteria have been tested for their capacity to transport the fungal spores, P. vortex is the most efficient, and it can disperse the spores across large distances (up to 30 cm). The flagellar interaction with the spores is abrogated by perturbations to the protein coat, which also possesses a rodlet layer. In exchange for spore dispersal, the swarming P. vortex is able to cross air gaps due to 'bridges' formed by elongated fungal hyphae, and can thus occupy new niches [18.Inghama C.J. et al.Mutually facilitated dispersal between the nonmotile fungus Aspergillus fumigatus and the swarming bacterium Paenibacillus vortex.Proc. Natl. Acad. Sci. U. S. A. 2011; 108: 19731-19736Crossref PubMed Scopus (65) Google Scholar].Indeed, several studies have found that various species of fungi and bacteria comigrate across so-called 'fungal highways' that span air gaps [26.Kohlmeier S. et al.Taking the fungal highway: Mobilization of pollutant-degrading bacteria by fungi.Environ. Sci. Technol. 2005; 39: 4640-4646Crossref PubMed Scopus (257) Google Scholar, 27.Warmink J.A. Hitchhikers on the fungal highway: The helper effect for bacterial migration via fungal hyphae.Soil Biol. Biochem. 2010; 43: 760-765Crossref Scopus (113) Google Scholar, 28.Warmink J.A. Van Elsas J.D. Migratory response of soil bacteria to Lyophyllum sp. strain Karsten in soil microcosms.Appl. Environ. Microbiol. 2009; 75: 2820-2830Crossref PubMed Scopus (99) Google Scholar]. In these instances, bacteria use their intrinsic motility to cross the mycelia bridges. To date, transport of fungal spores by these species has not been reported. However, there is evidence that bacterial migration may be facilitated by first actively attaching to the tip of emerging fungal hyphae using a type III secretion system. They are then translocated along with the growing hyphae [27.Warmink J.A. Hitchhikers on the fungal highway: The helper effect for bacterial migration via fungal hyphae.Soil Biol. Biochem. 2010; 43: 760-765Crossref Scopus (113) Google Scholar,28.Warmink J.A. Van Elsas J.D. Migratory response of soil bacteria to Lyophyllum sp. strain Karsten in soil microcosms.Appl. Environ. Microbiol. 2009; 75: 2820-2830Crossref PubMed Scopus (99) Google Scholar]. Collectively these studies suggest that fungi and bacteria may act alternatively as transporter and hitchhiker at various stages of their comigration.Bacterial Transport by ProtozoansThere have been reports of bacterial hitchhiking with protozoans that occur by internalization or direct attachment to the surface of the organism. The former mechanism is illustrated by the interaction of the pathogenic bacterium Legionella pneumophila with its amoebae hosts [21.Rowbotham T.J. Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae.J. Clin. Pathol. 1980; 33: 1179-1183Crossref PubMed Scopus (712) Google Scholar]. Motile L. pneumophila is found in aquatic environments, either in a free-living state or residing inside aquatic amoebae (e.g., Acanthamoeba and Naegleria), within which the bacteria replicate. Although infected amoebae present 'sickly' phenotypes, microscopic examination shows that they remain motile and carry the internalized L. pneumophila (Figure 1F) [21.Rowbotham T.J. Preliminary report on the pathogenicity of Legionella pneumophila for freshwater and soil amoebae.J. Clin. Pathol. 1980; 33: 1179-1183Crossref PubMed Scopus (712) Google Scholar].Hitchhiking mechanisms with protista can also be symbiotic, as seen with the interaction between aquatic Deltaproteobacteria and Excavata (Symbiontida and Euglenozoa) [29.Monteil C.L. et al.Ectosymbiotic bacteria at the origin of magnetoreception in a marine protist.Nat. Microbiol. 2019; 4: 1088-1095Crossref PubMed Scopus (38) Google Scholar]. The Deltaproteobacteria are capable of synthesizing intracellular ferrimagnetic nanoparticles, which are utilized by magnetotactic bacteria – bacteria that can sense magnetic fields and move in response to them [30.Yan L. et al.Magnetotactic bacteria, magnetosomes and their application.Microbiol. Res. 2012; 167: 507-519Crossref PubMed Scopus (150) Google Scholar]. However, the Deltaproteobacteria are nonmotile. Although the bacteria do not possess their own motility system, they attach themselves to the surface of the protist so that the linear ferrimagnetic particles are aligned to its motility axis, effectively making the protist magnetotactic (Figure 1G) [29.Monteil C.L. et al.Ectosymbiotic bacteria at the origin of magnetoreception in a marine protist.Nat. Microbiol. 2019; 4: 1088-1095Crossref PubMed Scopus (38) Google Scholar]. This may allow the resulting consortium of organisms to move toward niches with favorable redox and chemical environments while the bacteria also are protected from protozoan predators.Drawing Insights and Parallels among Hitchhiking MechanismsIn the instances of microbe–microbe transport discussed here, many motile partners are chemotactic, including: P. vortex [31.Shklarsh A. et al.Collective navigation of cargo-carrying swarms.Interface Focus. 2012; 2: 786-798Crossref PubMed Scopus (20) Google Scholar], A. baylyi [32.Li H. et al.Quantification of chemotaxis-related alkane accumulation in Acinetobacter baylyi using raman microspectroscopy.Anal. Chem. 2017; 89: 3909-3918Crossref PubMed Scopus (19) Google Scholar], P. aeruginosa [33.Moulton R.C. Montie T.C. Chemotaxis by Pseudomonas aeruginosa.J. Bacteriol. 1979; 137: 274-280Crossref PubMed Google Scholar], E. coli [34.Mesibov R. Adler J. Chemotaxis toward amino acids in Escherichia coli.J. 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Hitchhiking to such motile partners may effectively allow the nonmotile microbes to utilize the chemotaxis machinery of their host to reach their preferred microenvironment. A clear example of this is the Streptomyces spores that are produced on the soil surface but germinate and thrive near nutrient-rich plant roots that attract their transporters [19.Muok A.R. et al.Microbial piggy-back: how Streptomyces spores are transported by motile soil bacteria.bioRxiv. 2020; (Published online June 18, 2020. 10.1101/2020.06.18.158626)Google Scholar,39.van der Meij A. et al.Chemical ecology of antibiotic production by actinomycetes.FEMS Microbiol. Rev. 2017; 41: 392-416Crossref PubMed Scopus (187) Google Scholar].Since hitchhikers can utilize the motility machinery of other microbes, the question arises whether some nonmotile bacteria have 'chosen' not to evolve their own motility machinery and instead evolve hitchhiking mechanisms. Although there is no evidence for this specific idea yet, there are reports of microbes that may have lost their motility machinery because it is metabolically costly and no longer necessary [40.Li Y. et al.On the energy efficiency of cell migration in diverse physical environments.Proc. Natl. Acad. Sci. U. S. A. 2019; 116: 23894-23900Crossref PubMed Scopus (22) Google Scholar,41.Lane N. Martin W. The energetics of genome complexity.Nature. 2010; 467: 929-934Crossref PubMed Scopus (705) Google Scholar]. For instance, the spores of some fungi, called zoospores, as well as spores of the bacterium Actinoplanes missouriensis, are flagellated and chemotactic to enable dispersal [42.van de Vossenberg B.T.L.H. et al.Comparative genomics of chytrid fungi reveal insights into the obligate biotrophic and pathogenic lifestyle of Synchytrium endobioticum.Sci. Rep. 2019; 9: 1-14Crossref PubMed Scopus (16) Google Scholar, 43.Islam T. Tahara S. Chemotaxis of fungal zoospores, with special reference to Aphanomyces cochlioides.Biosci. Biotechnol. Biochem. 2001; 65: 1933-1948Crossref PubMed Scopus (41) Google Scholar, 44.Uchida K. et al.Characterization of Actinoplanes missouriensis spore flagella.Appl. Environ. Microbiol. 2011; 77: 2559-2562Crossref PubMed Scopus (22) Google Scholar]. But upon germination, the organisms no longer express motility proteins as they are not needed for survival [42.van de Vossenberg B.T.L.H. et al.Comparative genomics of chytrid fungi reveal insights into the obligate biotrophic and pathogenic lifestyle of Synchytrium endobioticum.Sci. Rep. 2019; 9: 1-14Crossref PubMed Scopus (16) Google Scholar, 43.Islam T. Tahara S. Chemotaxis of fungal zoospores, with special reference to Aphanomyces cochlioides.Biosci. Biotechnol. Biochem. 2001; 65: 1933-1948Crossref PubMed Scopus (41) Google Scholar, 44.Uchida K. et al.Characterization of Actinoplanes missouriensis spore flagella.Appl. Environ. Microbiol. 2011; 77: 2559-2562Crossref PubMed Scopus (22) Google Scholar]. Additionally, bioinformatics studies of the Methylophilaceae family of bacteria reveal that ancestors of these microbes were motile and chemotactic but as they evolved to occupy a new niche, those genes became inactive [45.Salcher M.M. et al.Evolution in action: habitat transition from sediment to the pelagial leads to genome streamlining in Methylophilaceae.ISME J. 2019; 13: 2764-2777Crossref PubMed Scopus (38) Google Scholar].Microbial hitchhiking occurs by four general mechanisms. Remarkably, the hyperswarmer P. vortex seemingly employs three of them: potential pushing of antibiotic-resistant cargo [23.Finkelshtein A. et al.Bacterial swarms recruit cargo bacteria to pave the way in toxic environments.mBio. 2015; 6: 1-10Crossref Scopus (48) Google Scholar], cell body interaction with X. perforans [17.Hagai E. et al.Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces.ISME J. 2014; 8: 1147-1151Crossref PubMed Scopus (48) Google Scholar] (in the form of rafts), and attachment of spores to P. vortex flagella [18.Inghama C.J. et al
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