THE ABOVE LEFT PHOTO shows enrichments in Mineral Salts-Succinate Broth (medium formula ) showing the characteristic "bloom" after about a week of incubation in the light at 30°C. So here is a good question: After filling the bottles completely with sample and medium, how are anaerobic conditions actually achieved? Hint: What bacterial process (associated with energy generation) is responsible for "using up" the oxygen? (The large bottle on the right is not filled to the top but it has a layer of mineral oil floating on the medium. The same answer to the above question will apply here as well.)
We also do a test that is somewhat similar in its setup (but not so much in theory) to the which utilizes Thioglycollate Medium. In Thioglycollate Medium, it is important to recall that is due only to fermentation. However, in the particular test considered here for the purple non-sulfur photosynthetic bacteria, anaerobic growth is only associated with anoxygenic phototrophy, and the categories associated with the standard oxygen relationship test (strict aerobe, facultative anaerobe, etc.) do not apply.
This light-dependent behavior of anthocyanin-coloured flowers cannot be explained within the pollinator-attraction hypothesis but seems to be in accordance with the proposed antioxidative protective role of these pigments. However, reactive oxygen species (ROS) are generated mainly as by-products of photosynthesis in chloroplasts or of respiration in mitochondria. Chloroplasts are absent or almost absent from flower petals. Regarding respiration, ROS must be scavenged by anthocyanins before these antioxidants have been transported from the cytoplasm, begging the question as to what the colored anthocyanins do when they are stored in the vacuole. Moreover, the increase of anthocyanins obviously results in additional light absorbance and heating that, in turn, can have the opposite effect: a stress-induced increase of ROS production. In general, one can agree with Hatier J.-H. and K. Gold, that “the fate of these absorbed quanta is unknown…”, stating that the physiological significance of anthocyanins in flower petals is not completely understood.
The photoacoustic studies in the present work demonstrate that the light energy that is absorbed by blue chlorophylless P. hybrida flower petals is partially utilised for the photochemical processes (ES > 0), but the evolution of oxygen was not revealed by gas-exchange measurements. We found that the respective anthocyanin-dependent, anoxygenic photosynthesis in flower petals (ADAPFP) is accompanied by a photoinduced increase in the ATP level. In seeking potential ADAPFP-related subcellular structures, we developed a simple adhesive-tape stripping technique, that was used to obtain a backside image of an intact monolayer of flower petal epidermis, revealing sword-shaped ingrowths, that connect cell wall with vacuole.
An example of chlorophylless photosynthesis, based on the redox chain mechanism, was recently shown to be dependent on light absorption by the green fluorescent protein (GFP) in jellyfish. The authors demonstrated the photoinduced electron transfer from GFP to tetrazolium, quinone, FMN+ and NAD+. A carotenoid-dependent, chlorophylless photosynthesis was shown in aphids. The carotenoid-containing aphids with an orange phenotype (in contrast to a greenish phenotype) exhibited a light-dependent increase in the NADH/NAD+ ratio and ATP content, and their extracts were also able to perform the photoinduced reduction of tetrazolium. In this connection, it was proposed that the photosynthetically reduced NADH was being utilised as an external electron donor by the mitochondria for ATP synthesis using known pathways. Both of these proposed types of photosyntheses, GFP-based and carotenoid-based, can be reliably interpreted in terms of redox chain mechanisms as the photosynthetically synthesised reducing equivalents originate from the cytoplasm and are easily transported to the mitochondria.
Chlorophylless flower petals are known to be composed of non-photosynthetic tissues. Here, we show that the light energy storage that can be photoacoustically measured in flower petals of Petunia hybrida is approximately 10-12%. We found that the supposed chlorophylless photosynthesis is an anoxygenic, anthocyanin-dependent process occurring in blue flower petals (ADAPFP), accompanied by non-respiratory light-dependent oxygen uptake and a 1.5-fold photoinduced increase in ATP levels. Using a simple, adhesive tape stripping technique, we have obtained a backside image of an intact flower petal epidermis, revealing sword-shaped ingrowths connecting the cell wall and vacuole, which is of interest for the further study of possible vacuole-related photosynthesis. Approaches to the interpretations of ADAPFP are discussed, and we conclude that these results are not impossible in terms of the known photochemistry of anthocyanins.
Unfortunately, photoacoustic (PA) spectrometry is the only direct method for revealing and studying CET (as anoxygenic photosynthesis). The PA method is based on the measurement of acoustic signals that are excited in test samples using a modulated light. If photochemistry is not occurring in a sample, the absorbed light is converted to heat, providing the photothermal component of the PA-signal with an efficiency of 100%. Otherwise, the light energy becomes partially unavailable for conversion as it is stored as photochemical products,. In this case switching on a strong background (non-modulated) light saturates the photochemistry, and the acoustic signal amplitude increases with a value equal to that of the energy storage (ES). Such an increase occurs only when the photobaric component is eliminated,. Considering the kinetic and spectral parametres of the PA-signal, a nonzero ES value provides an incontrovertible and direct evidence of either oxygenic or anoxygenic photosynthesis,,.
b)What is the function of these pigments? To harvest light energyand funnel it to the reaction center (the "special" chlorophyll molecules)c) What advantage is it to phototrophs in the environment to have evolvedmany different kinds and colors of pigments? It allows them to competefor different portions of the visible light spectrum, because the differentpigments absorb different wavelengths of light20)--Fill in the blanks:In anoxygenic photosynthesis, LIGHT excites a specialpair of electrons found in A SPECIAL CHLOROPHYLL MOLECULE toa lower reduction potential.
In contrast to flower petals, the green leaves P. hybrida revealed another (well-known and expected) behaviuor of PA signal response under different modulating frequencies (40 and 280 Hz; ). At 40 Hz, dark CTP results in a PA-signal increase, but at 280 Hz it results in a decrease (ES = 12.7%). The conventional interpretation of the photoacoustic activity of chlorophyll-containing tissues assumes that at low frequencies (up to 100 Hz) the PA signal reflects primarily its “photobaric” component which is currently mostly explained in terms of pulsed photosynthetic oxygen evolution. The photobaric component is in antiphase with the photothermal component. At higher frequencies (>150 Hz), the evolution of oxygen becomes continuous and does not contribute to the PA signal allowing the photothermal component to dominate. Thus, when dark CTP interrupts strong continuous light, photosynthesis exits saturation mode, and the efficiency of the oxygen evolution under modulating light and consequent PA signal increase. Under the same conditions, but at high modulating frequencies in which the photobaric component is absent, the absorbed light energy is converted to chemical energy more effectively, and the PA signal decreases.
Anoxygenic (no oxygen), elemental sulfur or other sulfur compounds, ororganic compounds can replace O2 as the end product.19) Different phototrophic Bacteria have evolved different light-absorbingantenna pigments.a) List the major types or pigments and indicate which group of phototrophsthey are found in.
Direct evaluations of the differential PA signal shape were calculated by the subtraction of two signals that were measured before and after continuous strong light switching, each averaged over 100 individual pulses (). The results demonstrate that the differential signal (photodependent response) has a short time delay to the amplitude maximum of less then 0.7 ms (, blue curve). For comparison, the same parametre calculated for the photobaric component of green leaves is approximately 3 ms reflecting the photosynthetic oxygen evolution. However, this delay for the flower petals is too low to be ascribed to gas evolution, and therefore, the obtained differential signal is a time function of the energy storage, indicating some unknown rapid photochemical process which is competing with photothermal dissipation to utilise light energy.