Several lines of evidence indicate that this newly discovered bacterial symbiont of the attine ants is a third mutualist in an ancient symbiosis among the ants, the domesticated fungi, the parasitic fungi, and the antibiotic-producing bacteria
CONTENT: activity of the newly found bacteria in the ants connects to previously identified bacteria that connect to the symbiotic processes of ants in terms of antibiotic production
before mating flights revealed the presence of the cuticular actinomycete on females only (n = 74 ants, including 43 males, from 10 colonies). Because males do not participate in the founding of new colonies or in tending the fungal garden, these data support the proposed role of the actinomycete in suppressing the growth of garden pathogens.
CONTENT: The bacteria is found more in females than males because the females are the ones that do the harvesting of the soil, exposing them more to the invasive bacteria.
We studied the presence of the actinomycete on foundress queens (gynes) during their mating flights to determine whether, like the fungal mutualist, this bacterium is transmitted vertically between parent and offspring colonies.
CONTENT: The bacteria spreads vertically between ants when they mate, and they are able to be passed from parent to offspring
(Fig.2c),
FORM: Citing findings and information with reference to the visuals displayed above
The bacterium was associated with allspecies studied, from the phylogenetically basal genera Myrmicocrypta and Apterostigma to the highly derived, leaf-cutting genera Acromyrmex and Atta. All 112 colonies from Panama sampled for the presence of the actinomycete in 1997 and 1998 showed this bacterial association. In all cases, the actinomycete was concentrated on genus-specific areas of the ant integument that appear to be modified for the maintenance and growth of the Streptomyces, conceivably to facilitate the distribution of bacterial metabolites throughout the garden
CONTENT: The experiments held concluded that this bacteria was found in all of the sample species that were studied, making the previously unknown function of the bacteria identified throughout the species
a
CONTENT: The spread of the Streptomyces is shown from a microscopic point of view, displaying the process of spreading to eventually control the functions of the ant
of the genus Streptomyces (Fig. 2a; see Methods). Actinomycetes are mostly soil-dwelling organisms of great abundance and ecological importance that produce an array of secondary metabolites, many of which have specific antibacterial or antifungal properties11,12.
CONTENT: The standard language ideology is used to help define how this bacteria is used to attract the ants in the soil and latch to them in order to control their bodies, making them essentially "zombies", since their functions are being controlled
Certain areas of the cuticle of fungus-growing ants are coated with what appears to the naked eye to be a powdery, whitish-grey crust (Fig. 1). This has been dismissed previously as a ‘waxy bloom’, implying that its aetiology was cuticular exudate
CONTENT: The biological appearance of function of these ants have been mislabeled previously, but that has now been experimented on to define the function. This aligns with the inquiry of the article about how different parts of the ant are affected by the fungus.
Because few organisms cultivate their own food, fungus-gardening by ants (Attini: Formicidae) is considered to be a major breakthrough in animal evolution
CONTENT: Through evolution, many organisms, such as these fungus-eating ants, have needed to harvest their own food, which happens to be an invasive parasitic fungus that manages to take over their bodies
References
FORM: Credit given to others within the discourse community that contributed to the new findings in the field.
Each Streptomyces –fungal challenge was replicated three times and done on Czapek yeast autolysate agar. The actinomycete was inoculated on Petri dishes and grown to a diameter of ∼1.5 cm; fungal strains were then point-inoculated near the edge of the culture. Challenges were monitored every two days and growth inhibition of tested fungi was scored as a reduction of growth rate as compared with growth of fungal cultures in the absence of the Streptomyces, or as complete suppression of growth. We assayed possible antibiotic production specific to the specialized parasite Escovopsis in the same way that we assayed antibiotic production specific to other potential contaminants, except that each challenge to Escovopsis was replicated five times. Four strains of Escovopsis isolated from the gardens of different Acromyrmex octospinosus colonies in Panama in 1997 were tested against Streptomyces. We also studied the production of antibiotics specific towards Escovopsis in other attine species, including Cyphomyrmex longiscapus, Atta colombica and Atta cephalotes. The presence of a zone of inhibition in bioassays indicates first, the production of diffusible metabolites by the actinomycete, and second, the susceptibility of the test fungus to these compounds. As inhibition is dose dependent, the detection of partial inhibition
FORM: Heavy amount of lexis that caters to the discourse community, making this a scholarly article aimed particularly at those with previous knowledge in the field.
Methods
FORM: Steps that are used to obtain the information in the article are defined using the lexis of the discourse community.
Although the ant–fungus mutualism is often regarded as one of the most fascinating examples of a highly evolved symbiosis, it is now clear that its complexity has been greatly underestimated. The attine symbiosis appears to be a co-evolutionary ‘arms race’ between the garden parasite, Escovopsis, on the one hand, and the tripartite association amongst the actinomycete, the ant hosts, and the fungal mutualist on the other.
FORM: Why the findings are important to the DC
Bioassay challenge between Streptomyces and Escovopsis, the specialized parasite of attine fungal gardens, associated with Acromyrmex octospinosus,
FORM: Defining findings and terms
, View of the filamentous growth form of the actinomycetous bacterium, showing the typical growth pattern and its thickness on the cuticle. Scale bar represents 10 µm. b, View of Streptomyces (arrow) under the forelegs of Apterostigma sp; this is the characteristic location of the bacterium in phylogenetically basal genera of the Attini. Scale bar represents 100 µm. c, Ventral view of a minimum worker of Acromyrmex octospinosus. The actinomycete-laden laterocervical plate (arrow) can be seen just below the head on the propleura of the ant. This is the characteristic location of the bacterium on the more phylogenetically derived genera of the Attini. Scale bar represents 500 µm.
FORM: The mode of the article consists of multiple up-close views of the process within the ants that in being studied, further clarifying the line of inquiry suggested by the author
Other lepiotaceous lineages, and in one case a distantly related non-lepiotaceous basidiomycete, were domesticated in subsequent evolutionary history4. The success of fungal cultivation by the attine ants is illustrated by the leaf-cutting genera, Acromyrmex and Atta, which are the dominant herbivores in the neotropics9
FORM: Specific lexis is used from the DC community in order to explain the concept in terms familiar to the group
)3,4,8.
FORM: Source trail to give credit to previous findings from other members of the DC
lthough it is thought at present to involve only two symbionts, associated with each other in near isolation from other organisms1,5, the fungal gardens of attine ants are in fact host to a specialized and virulent parasitic fungus of the genus Escovopsis (Ascomycotina)6. Because the ants and their fungi are mutually dependent, the maintenance of stable fungal monocultures in the presence of weeds or parasites is critical to the survival of both organisms. Here we describe a new, third mutualist in this symbiosis, a filamentous bacterium (actinomycete) of the genus Streptomyces that produces antibiotics specifically targeted to suppress the growth of the specialized garden-parasite Escovopsis
FORM: Introduction that summarizes previous knowledge about the subject, using specific Latin names of the species in order to adequately define the material that was studied.
Cameron R. Currie1,2, James A. Scott2, Richard C. Summerbell3,4 & …David Malloch2
FORM: Authors that contributed to the DC and who collaborated on the new information below
Fungus-growing ants use antibiotic-producing bacteria to control garden parasites
FORM: Title to display a quick summary of findings and what the article is about