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Häkkänen, H.

Publications and source records attributed to Häkkänen, H..

2 recordsLinked to original sources
bioRxiv2023

NIRis: A low-cost, versatile imaging system for NIR fluorescence detection of phototrophic cell colonies used in science and education

A variety of costly research-grade imaging devices are available for the detection of spectroscopic features. Here we present an affordable, open-source and versatile device, suitable for a range of applications. We provide the files to print the imaging chamber with commonly available 3D printers and instructions to assemble it with easily available hardware. The imager is suitable for rapid sample screening in research, as well as for educational purposes. We provide details and results for an already proven set-up which suits the needs of a research group and students interested in UV-induced near-infrared fluorescence detection of microbial colonies grown on Petri dishes. The fluorescence signal confirms the presence of bacteriochlorophyll a in aerobic anoxygenic phototrophic bacteria (AAPB). The imager allows for the rapid detection and subsequent isolation of AAPB colonies on Petri dishes with diverse environmental samples. To this date, 15 devices have been build and more than 7000 Petri dishes have been analyzed for AAPB, leading to over 1000 new AAPB isolates. Parts can be modified depending on needs and budget. The latest version with automated switches and double band pass filters costs around 350{euro} in materials and resolves bacterial colonies with diameters of 0.5 mm and larger. The low cost and modular build allow for the integration in high school classes to educate students on light properties, fluorescence and microbiology. Computer-aided design of 3D-printed parts and programming of the employed Raspberry Pi computer could be incorporated in computer sciences classes. Students have been also inspired to do agar art with microbes. The device is currently used in seven different high schools in Finland. Additionally, a science education network of Finnish universities has incorporated it in its program for high school students. Video guides have been produced to facilitate easy operation and accessibility of the device. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=62 SRC="FIGDIR/small/543100v2_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@6dfcb7org.highwire.dtl.DTLVardef@ea7fbcorg.highwire.dtl.DTLVardef@1681e78org.highwire.dtl.DTLVardef@a88d51_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗
bioRxiv2023

Aerobic anoxygenic phototrophic bacteria are ubiquitous in phyllo- and endosphere microbiomes of boreal and subarctic plants

In addition to oxygenic photosynthetic systems, solar radiation is utilized for energy by diverse anoxygenic photosynthetic systems. Aerobic anoxygenic phototrophic bacteria (AAPB) perform photosynthesis without producing oxygen but still live in aerobic conditions. Typically they have been reported from aquatic ecosystems, but they can also be found from polar and desert soil ecosystems and primary succession communities like soil crusts. Recently, AAPB have been discovered in the metagenomic data of several plant phyllospheres. By utilizing citizen science, we screened plant foliar samples from eleven different locations in Finland for AAPB by near infrared fluorescence imaging of culturable phyllosphere and endosphere bacteria. Near infrared fluorescence reports the presence of AAPB which contain Bacteriochlorophyll a molecules, embedded in Light Harvesting 1 - Reaction Center complex. We found that AAPB were ubiquotous in phyllosphere communities of diverse plant species in all sampling locations. They were also consistently present in the endosphere of plant species with perennial leaves. Most of the AAPB isolated represent alphaproteobacterial genera Sphingomonas and Methylobacterium, but several isolates from genus Lichenihabitans as well as putative novel alphaproteobacterial taxa were also identified. Methylobacterial isolates were mostly detected in the phyllosphere with weak host specificity, while Sphingomonas AAPB were detected also in the endosphere of several plant species, with clear host specific taxa. We studied also the fluorescence spectral properties of several AAPBs. All the observed spectra resemble typical fluorescence spectral properties of Light Harvesting complex 1. Still, slight variation among each spectra could be obtained, revealing some physical difference among the complexes. Our results demonstrate for the first time, that AAPB are common in cold climate plant endophytic as well as epiphytic microbiomes and they build up substantial amounts of Bacteriochlorophyll a containing Light Harvesting complexes. Their putative role in plant adaptation to strong seasonality in light and temperature or tolerance of abiotic stressors remains to be investigated in future studies.

microbiology↗