The fruiting bodies have varied shapes. Some, like Polyporus arcularius , consist of a cap on a stem but most polypores are either bracket-like in form such as Ganoderma australe and Phaeotrametes decipiens or, like Macrohyporia dictyopora , more-or-less sheet-like and pressed closely to the underlying wood.
The corticioid and stereoid fungi have basidia lining the undersides of the fruiting bodies. The corticioid fungi have sheet-like fruiting bodies - often smooth but also found with minor bumps, ridges, spines, etc on the otherwise two-dimensional sheets. The stereoid fruiting bodies also have generally smooth undersides but are bracket-like or with a stem - and therefore differ from the corticioid fungi by being markedly three-dimensional. The following diagram, represents a corticoid fruiting body the brighter brown growing on the underside of a piece of wood lying on the ground.
You can see the basidia protruding into the air. A funnel-shaped stereoid fungus such as Cymatoderma elegans var.
In a coral fungus, such as Clavaria zollingeri the basidia are found on many of the branches, as shown in this diagram. The irregularly shaped jelly fungi such as the species of Tremella have the basidia in the convoluted surfaces of the fruiting bodies. In contrast to the fungi described above, the basidia of the jelly fungi are within the gelatinous fruiting body, with only the ends of the sterigmata and the spores protruding into the air.
The basidia and hyphae that make up the fruiting bodies are often embedded within a gelatinous matrix that can make the hyphae hard to see. In this diagram the dull yellowish colour represents the gelatinous matrix and the thick, grey, wavy lines are the hyphae of the fruiting body. As before, the basidia and spores are coloured green and brown respectively. The fresh fruiting bodies of species in the genus Auricularia are gelatinous and somewhat ear-shaped hence the common name of Wood Ears, for they grow on wood.
The basidia are elongated, tapering at their ends and septate across their width. As in the jelly fungi, the basidia of Auricularia are within the fruiting bodies with just the ends of the sterigmata and the spores beyond the surface.
The basidia are in the smooth, semi-glossy undersurface - not the dull, roughened to bristly upper surface. This diagram shows the arrangement in Auricularia , using the same colour code as in the preceding jelly fungus diagram.
The fruiting bodies of the basidiomycete truffle-like fungi are varied in form, sometimes stalked but mostly stalk-less and more-or-less spherical in shape. Internally the fruiting bodies are chambered, with the chambers of some species easy to see with the naked eye - but a hand lens is needed to see the individual chambers in other species.
The basidia line the walls of the chambers and protrude into the interiors of the chambers - which are empty in many species, but not in all. In shape the chambers may be anything from spherical to quite contorted. This diagram represents the cross-section of a truffle-like fruiting body. The solid, fleshy areas of the truffle are coloured brown and you can see the basidia coloured green and bearing dark brown spores lining the walls of those chambers.
Of course, this diagram exaggerates the sizes of both the basidia and the chambers and this simplistic two-dimensional figure does not do justice to the internal convolutions of three-dimensional fruiting body. The photograph of the stalked Setchelliogaster fruiting body may give you a better idea of the internal structure.
On the left you can see the outside appearance and on the right the internal structure. In the latter you can see some of the chambers of varied forms and get an idea of the intricate way in which the internal tissue creates those chambers. In all of the preceding basidiomycetes the basidia are persistent.
Even by the time a mushroom has largely rotted away you can usually still find basidia on the gills. There are several common groups of basidiomycetes where the mature fruiting body has spores - but no basidia.
To find the basidia you must have an immature but not too young! Examples of such fungi are various powdery spored fruiting bodies the puffballs and similar fungi , the slimy-spored stinkhorns and the Bird's Nest Fungi. These are examples of a subgroup of the basidiomycetes commonly called the gasteromycetes.
The word gasteromycete literally means "stomach fungus" - and these fungi produce their spores inside the fruiting body that, at least initially, is enclosed within an outer skin.
While, as a group, these fungi may all be referred to as gasteromycetes, that name does not signify close evolutionary relationships between all the members. The name is simply one of convenience - rather than being one of classificatory importance. Reflecting their diverse origins, these fungi show considerable variation in both the overall appearance and internal structure of the immature, basidia-bearing fruiting bodies.
Many start as more-or-less spherical masses of homogenous tissue, and then develop various patterns of internal spore-bearing areas.
In some species these spore-bearing areas consist of empty cavities, with the basidia lining the walls and protruding into the empty interiors. In others the spore bearing areas may be filled with basidia and hyphae or a gelatinous matrix while the spores are developing. Pisolithus is a common powdery-spored gasteromycete genus, with the fruiting bodies often seen pushing up through bitumen roads.
Pisolithus sp. A vertical cross-section of such a fruiting body shows a powdery region at the top, but with the lower part looking as though it consisted of a multitude of densely packed rice grains called peridioles , comprising packets of spores.
The peridioles are relatively thin skinned and the whole mass is contained in a brittle outer skin. This highly stylized diagram shows a vertical cross-section through a very immature Pisolithus fruiting body.
The black circle represents the outer skin, the internal tissue is in brown and there are numerous chambers shown in white. Each of these chambers eventually becomes the interior of a peridiole.
These chambers are isolated from each other and contain the basidia. The chambers fill quickly with a gelatinous matrix, the spores become detached from their basidia and complete their development after detachment within the gelatinous interior.
Of course, in most cases people only see the Pisolithus fruiting bodies in the advanced, powdery stage as shown in the photograph. The mature fruiting body of a Bird's Nest Fungus such as this Cyathus novae-zealandiae consists of a leathery, cup-like structure that contains a number of disc-shaped "eggs" peridioles again.
These peridioles differ from the Pisolithus peridioles by being enclosed in a thick outer casing and by becoming separated from each other. The cup-like structure is usually no more than a centimetre in diameter at the top. Before the Cyathus fruiting bodies are mature, they have a membrane across the top of the cup. You can see a couple of immature fruiting bodies at the right in the photograph.
The following diagram shows an immature cup, cut away to show it full of peridioles. The figure on the right shows the basidia in the central part of one such peridiole. The thick brown line represents the peridiole's hard outer casing. At a young stage, the interior of a peridiole has a gelatinous filling and at an even younger stage the fruiting body would have had the same type of chambered appearance as shown in the stylized diagram for Pisolithus.
The preceding cross-section diagram shows a very simple type of internal structure, but numerous gasteromycetes have much more complicated patterns of development. Many mature puffballs have a very simple structure.
There's just a thin-walled sack of powdery spores with a hole at the top, through which the spores are puffed out when the sack is compressed. This simplicity at maturity belies the complex internal structure of the immature fruiting body during spore production.
At that stage the fruiting body has a very convoluted interior. The diagram represents a stylized vertical cross-section of such a young puffball. Here the cavities are not formed as separate chambers, but within ingrowths of tissue from the periphery. The basidia develop on those convoluted surfaces, shown here in brown. The fruiting bodies of stinkhorns in the genera Dictyophora , Mutinus and Phallus consist of a stem with the slimy spore mass on a small cap at the top of the stem.
The cap isn't spread out like a typical mushroom but hugs the stem fairly closely. In this picture of Dictyophora multicolor you can see the small, slimy cap. In addition, there is a mesh-like skirt that hangs down below the cap. This picture of a dissected Phallus rubicundus shows the cap a little more clearly. In line with the style of the two gasteromycete diagrams above, the following diagram represents a vertical cross-section of a young stinkhorn from any of the three genera listed above.
You can see the unexpanded stem, the curved cap and the short projections growing in from the marginal tissue that bear the basidia. It is important to realize that, as in the case of the truffle-like diagram above, these gasteromycete diagrams are also very simplistic, two-dimensional representations of considerable three-dimensional complexity. Looking more closely at the young stage of Dictyophora , here is a more detailed but still stylized diagram of the structure, showing an enlarged view of the area contained within the blue rectangle above.
The young stinkhorn is enclosed within a thin, leathery skin, represented here by the thin dark-grey line. Immediately beneath that skin is a relatively broad gelatinous zone the stippled band.
The projections can form quite intricate channels and chambers but once the spores have matured they break down into the smelly, khaki to brown slime that holds the spores on the outside of the cap of the mature fruiting body.
The stem-and-cap type of development as shown above in the simple brown diagram is not restricted to stinkhorns. The powdery spored Podaxis pistillaris also has such a form when young. In the mature stage Podaxis fruiting bodies look like powdery drumsticks. Thickness measurements of the sCMMs resulted in a mean width of 5. Representative images from the membrane thickness analysis are shown in Supplementary Fig.
A Cross-section through an entire spore, which shows sub-core membrane membranes sCMMs; arrows in the core, directly below the CM cm. C Partial view of a tangential section through a dormant spore almost parallel to the long axis of the spore and directly below the inner surface of the CM see inset for a schematic illustration of the level of sectioning. At this section plane, numerous double-ring sCMMs with the periodic dark-bright-dark-bright-dark contrast are visible.
To facilitate further structural and functional analysis of the sCMMs within the core, we tested if we could find them in chemically fixed, plastic embedded spores. Cryo-preparation methods, such as high-pressure freezing and freeze-substitution, do not preserve the core of dormant spores 9.
In thicker sections i. Since the visibility of the sCMMs seemed to correlate with the section thickness the thinner the section, the sharper the contrast , we recorded tomographic tilt series of thin sections and computed tomograms. In digital sections of such tomograms, the sCMMs mostly showed the periodic contrast which was already observed by CEMOVIS and which suggests the presence of closely apposed double-membrane layers Fig.
However, we never observed a direct membrane connection between the spore core membrane and sCMMs, something which would be expected in case of a persisting invagination of the core membrane. Conventional thin section electron microscopy of dormant B. A Cross-section and B longitudinal section.
C Enlarged view of boxed area in B which shows that the membrane-like morphology is only partially visible and that the sCMMs exhibit a dark-bright-dark contrast. The analysis of serial sections taken parallel to the spore long axis, revealed no preferred localization of the sCMMs below the CM.
In other regions devoid of sCMMs, no other special structures could be observed Fig. However, tangential sections through the core reveal rather uniformly and densely distributed circular section profiles of sCMMs Supplementary Fig.
S2 , which supports the conclusion of a relatively ubiquitous presence of sCMMs below the CM of dormant spores. Distribution of sCMMs arrowheads within the core co of dormant B. A Section 4 and B section 5 of 10 serial sections through a dormant spore see Supplementary Fig.
S3 for all sections through the spore. Although the visibility of sCMMs decreased significantly during immunolabelling procedures, association of gold labelling with structures similar in size, shape and localization to sCMMs of the core was possible Fig.
Quantitation of the anti-SpoVAD labelling in comparison to the labelling of three control antibodies clearly suggested that the anti-SpoVAD labelling of the CM and of the adjacent core zone, in which the sCMMs are localized, was specific, because labelling with anti-SpoVAD in those regions was significantly higher difference at least 5-fold standard deviation of controls than with the control antibodies Fig.
In contrast, the observed labelling of the core was almost identical with anti-SpoVAD and control antibodies difference was smaller than one standard deviation of controls Fig. Immunogold labelling of sections through dormant spores of B.
A Longitudinal section through a spore which shows the general distribution of the gold particle labelling. Significant labelling is seen along the CM black arrowheads and in the zone below the CMc where the sCMMs white arrowheads are localized.
Note that the visibility of sCMMs is reduced in comparison to Figs 3 and 4 but their identification still is possible due to the reduced electron density of the structures in comparison to the central part of the spore core. The CM black arrowheads is strongly labelled and two of the three sCMMs white arrowheads are labelled. C Quantification of the labelling densities of the anti-SpoVAD labelling grey bars in comparison to labelling with three control antibodies white bars for the background and different core regions: 1 CM, 2 sCMM zone, 3 core, see Supplementary Fig.
Labelling densities of the three control antibodies are expressed as the mean of the labelling density distribution and error bars correspond to the SD. Morphological features of the sCMMs, such as contrast and width, and the localization of an abundant CM protein in them, indicate that these structures are membranes, like the CM. To get an idea about the function of the sCMMs, we analyzed their fate in germinating B. Spore germination in rich TSB medium was stopped at different time points by adding concentrated fixative.
After embedding in LR White resin and ultrathin sectioning, samples were investigated by transmission electron microscopy. As expected, dormant spores showed sCMMs Fig. With ongoing germination, the number of spores which show structural signs of germination, such as disintegration of the cortex and core swelling, increased.
Moreover, the sCMMs disappeared Fig. To get more precise information about the time course of sCMM disappearance, we measured the presence of sCMMs in relation to the core size during germination. While the relative core size core circumference relative to outer spore circumference in spore sections increased with germination time, the fraction of spore sections showing sCMMs decreased.
In summary, the obvious correlation between core expansion and disappearance of sCMMs suggests that the sCMMs are incorporated into the CM during core expansion in spore germination. Presence of sCMMs in spores of B. While sCMMs arrowheads can be seen in the dormant spore, the section through the germinating spore does not reveal any membrane structures with a similar morphology and location in its core. As expected, the core co of the germinating spore is much larger than the core of the dormant spore and the cortex cx appears thinner, less compact and rather filamentous.
C Relative core size and presence of sCMMs in sections through spores fixed at different times of spore germination in TSB medium 30 sections per time point were evaluated. The diagram shows an inverse correlation between relative core size core circumference divided by spore circumference and presence of sCMMs over time of germination. The fraction of spore sections showing sCMMs drops over time as the relative core size increases. See also Supplementary Fig. S4 for the time course of this germination experiment in phase-contrast light microscopy which shows that practically all spores had completed the transition from phase-bright to phase-dark during this period indicating at least the beginning of cortex degradation and core expansion stage II of germination.
To investigate whether the sCMMs in the core of dormant spores are a special feature of B. In spores of all of these species we could detect the sCMMs in the spore core within a distinct zone directly below the CM Fig. While the sCMMs in B. S5A and B.
S5B, C. However, sCMMs could be found in the core of spores at similar locations in all species studied. B , D show respective enlarged views of sCMMs arrowheads. See Supplementary Fig. S5 for images of more species. Thin section electron microscopy visualized sCMMs in the core of B. The presence of these sCMMs could be demonstrated by cryo-electron microscopy of vitreous sections CEMOVIS , which eliminates artifacts introduced by chemical processing 12 and by conventional electron microscopy using chemical fixation and plastic embedding.
Visualization of sCMMs in plastic-embedded samples was possible by using the hydrophilic acrylate resin LR White in combination with a particular staining approach for sections 13 which provides a mixture of positive and negative contrast. Interestingly, internal core membranes similar to the sCMMs could be demonstrated in spores of B. Conventional thin section electron microscopy using epoxy resin embedding and contrasting of sections with uranyl acetate and lead citrate provides rather positive contrast 15 and did not allow visualization of sCMMs.
Since this procedure is generally used for the analysis of spore ultrastructure, it appears obvious that the sCMMs have been widely overlooked so far. The visualization of sCMMs was dependent on section thickness and staining quality i. This discrepancy in membrane visibility can be explained by the different environmental conditions for the CM and the sCMMs.
In the dormant spore, core molecules and supramolecular structures e. In contrast, CaDPA is only present on one side of the CM, the core side, while the side facing towards the cortex is at least accessible for small molecules activating the germination receptors 5.
Apart from the morphological features, two other results indicate that the sCMMs are bio-membranes like the CM. The labelling in both zones by the anti-SpoVAD antibody was considered as specific based on a comparison with labelling by three control antibodies and therefore most likely represent the localization of SpoVAD.
Displacement of SpoVAD molecules from the CM into the sCMM zone caused by extraction during sample preparation, or displacement of the antibodies decorating the membrane, seem unlikely reasons for the observed labelling pattern because the cortex was not significantly labelled Fig.
Extraction and label displacement should be more uniform and not only directed towards the core. However, we cannot fully exclude the influence of these factors on the labelling result. It is also remarkable that the central core zone itself showed some labelling which was considered as rather nonspecific because control antibodies produced almost the same labelling density Fig.
However, it is possible that some SpoVAD molecules, which are quite hydrophilic 19 , are not incorporated into the SpoVA protein complex in spore membranes during sporulation and still reside within the core plasma.
Core expansion is a morphological hallmark of stage II during spore germination, in which full spore core rehydration and metabolic activity is restored 6 , Our morphological analysis of germination clearly shows that the relative core size in thin sections is increasing while at the same time the fraction of spore sections revealing sCMMs is decreasing.
However, this indicates that CaDPA was fully released by the spores and that the spore most likely entered stage II of germination and beginning cortex hydrolysis and core expansion 6 , 11 , which supports our observation of an increase in core size during this period of germination. The most intuitive explanation for the disappearance of the sCMMs is that these membranes were incorporated into the CM to facilitate the increase in CM surface area accompanying core expansion Fig.
From the serial section analysis Fig. Membrane fusion processes are extremely rapid 21 , 22 and difficult to capture. Perhaps experiments at a higher temporal resolution regarding the time course of germination and increasing the speed of fixation e. However, it is unclear how these two types of membranes are linked.
A Schematic representation of the morphological events in spore germination. The sCMMs arrowheads disappear in a period when core co expansion arrows and cortex cx lysis is taking place, consistent with sCMM integration into the CM cm during germination to allow core expansion.
A vesicular shape with a cup-like compressed membrane surface at one side would be sufficient to explain at least part of the sectioning profiles found and which are shown on the right side. Our analysis of the presence of sCMM in spores of different Bacillales and Clostridiales species suggests that sCMMs are a universal feature of spores. This is not unexpected, since much of the spore germination machinery and architecture providing spore resistance are universal in all Firmicute spore-formers 2 , 5.
Indeed, pan-species universality was recently shown for the crystalline organization of the DNA in the dormant spore which is an important factor for providing DNA resistance 9. However, while sCMMs were found in spores of all species, their section profiles were somewhat different in different species.
In spore of B. Ultimately, analysis of the sCMM 3D structure at higher resolution is needed to get more information about these membranes and their potential link to the CM. Cryo-tomography of slices prepared by cryo-focussed ion beam milling 23 , 24 , 25 may help to solve this issue when this technique becomes more widely available.
So far, we can only speculate about the 3D structure of the sCMMs. The most intuitive fit with the sectioning profiles detected by CEMOVIS this technique gives the most reliable structural representation suggests a 3D structure of a compressed vesicle or tubule Fig. This hypothesis would be in accordance with known membrane dynamics in cells mediated by fission and fusion of vesicles or small tubules. Growing on bark, decorticate wood or bryophytes on bark.
Growing on rock or bryophytes on rock or soil. Growing on bark. Growing on decorticate wood or on bryophytes at base of trees. Hypothecium or central part of exciple colorless or yellowish, KOH-; rim and outer part of exciple brown or colorless.
Thallus not granular, not papillose; apothecia dark. Apothecia yellowish or pale buff, with pruinose margin; granules not papillose; rare.
Apothecia pale orangish; thallus of isidioid granules; granules strongly papillose; only a single collection from Carter Co. Spores 2. Apothecia swollen; margin absent or obscured. Exciple of hyphae with narrow lumina, enlarged only in outermost cells. Francois Co. Apothecia brown; exciple in part brown; hymenium brown streaked; rare.
Apothecia whitish or pallid; apothecial tissues colorless; rare. On decorticate wood.
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