Microenvironment and bacterial community structure in the gut of wood- and litter-feeding cockroaches

While the gut microbiota of termites and its role in symbiotic digestion have been studied for decades, little is known about the bacteria colonizing the intestinal tract of detritivorous cockroaches. To improve the phylogenetic classification of short-read libraries, we first created a curated reference database of the bacterial 16S rRNA gene, based on the SILVA database and 1048 additional full-length 16S rRNA gene sequences from the intestinal tracts of 24 dictyopteran insects (chapter 2). The performance of the database in the classification of short-read libraries from termites and cockroaches was highly superior to that of the current SILVA and RDP databases. We then investigated the bacterial gut communities in the crop, midgut and hindgut of two xylophagous (chapter 3) and three litter-feeding (chapter 4) cockroaches by Illumina sequencing, and compared them to those in omnivorous cockroaches and termites, focusing on two main questions: First, if host diet determines the gut microbiota in cockroaches, and second, what role environmental variables play in different gut compartments. We found that the gut microbiotas of cockroaches share rare lineages and the phenomenon of gut compartment-specific communities with those of termites, but differ in community structure and show only little diet-specific distinction. In order to identify other potential drivers of microbial community structure in cockroach guts, we determined the intestinal physicochemical parameters pH, redox potential, and oxygen and hydrogen partial pressure. Surprisingly, the localization of intestinal hydrogen accumulation in the crop of two cockroach species differed from that in the posterior midgut observed previously for omnivorous species. Intestinal pH, in addition to other, yet unidentified factors, was a strong determinant of bacterial community structure, posing a strong selection pressure particularly in the hindgut compartment. For a better understanding of the digestion of lignocellulose by cockroaches in nature, I fed two cockroach species on oak leaf litter, and determined the degradation efficiency and metabolization rates of lignocellulosic fractions and carbohydrate monomers through controlled mass balances (chapter 5). I found that xylan rather than cellulose was degraded in the gut, suggesting that litter-feeding cockroaches preferentially degrade the easily solubilizable diet fractions like hemicelluloses

Dynamics of urinary and respiratory shedding of Severe acute respiratory syndrome virus 2 (SARS-CoV-2) RNA excludes urine as a relevant source of viral transmission

PURPOSE To investigate the expression of the receptor protein ACE-2 alongside the urinary tract, urinary shedding and urinary stability of SARS-CoV-2 RNA. METHODS Immunohistochemical staining was performed on tissue from urological surgery of 10 patients. Further, patients treated for coronavirus disease (COVID-19) at specialized care-units of a university hospital were assessed for detection of SARS-CoV-2 RNA in urinary samples via PCR, disease severity (WHO score), inflammatory response of patients. Finally, the stability of SARS-CoV-2 RNA in urine was analyzed. RESULTS High ACE-2 expression (3/3) was observed in the tubules of the kidney and prostate glands, moderate expression in urothelial cells of the bladder (0-2/3) and no expression in kidney glomeruli, muscularis of the bladder and stroma of the prostate (0/3). SARS-CoV-2 RNA was detected in 5/199 urine samples from 64 patients. Viral RNA was detected in the first urinary sample of sequential samples. Viral RNA load from other specimen as nasopharyngeal swabs (NPS) or endotracheal aspirates revealed higher levels than from urine. Detection of SARS-CoV-2 RNA in urine was not associated with impaired WHO score (median 5, range 3-8 vs median 4, range 1-8, p = 0.314), peak white blood cell count (median 24.1 × 1000/ml, range 5.19-48.1 versus median 11.9 × 1000/ml, range 2.9-60.3, p = 0.307), peak CRP (median 20.7~mg/dl, 4.2-40.2 versus median 11.9~mg/dl, range 0.1-51.9, p = 0.316) or peak IL-6 levels (median: 1442~ng/ml, range 26.7-3918 versus median 140~ng/ml, range 3.0-11,041, p = 0.099). SARS-CoV-2 RNA was stable under different storage conditions and after freeze-thaw cycles. CONCLUSIONS SARS-CoV-2 RNA in the urine of COVID-19 patients occurs infrequently. The viral RNA load and dynamics of SARS-CoV-2 RNA shedding suggest no relevant route of transmission through the urinary tract

Microenvironment and bacterial community structure in the gut of wood- and litter-feeding cockroaches

While the gut microbiota of termites and its role in symbiotic digestion have been studied for decades, little is known about the bacteria colonizing the intestinal tract of detritivorous cockroaches. To improve the phylogenetic classification of short-read libraries, we first created a curated reference database of the bacterial 16S rRNA gene, based on the SILVA database and 1048 additional full-length 16S rRNA gene sequences from the intestinal tracts of 24 dictyopteran insects (chapter 2). The performance of the database in the classification of short-read libraries from termites and cockroaches was highly superior to that of the current SILVA and RDP databases. We then investigated the bacterial gut communities in the crop, midgut and hindgut of two xylophagous (chapter 3) and three litter-feeding (chapter 4) cockroaches by Illumina sequencing, and compared them to those in omnivorous cockroaches and termites, focusing on two main questions: First, if host diet determines the gut microbiota in cockroaches, and second, what role environmental variables play in different gut compartments. We found that the gut microbiotas of cockroaches share rare lineages and the phenomenon of gut compartment-specific communities with those of termites, but differ in community structure and show only little diet-specific distinction. In order to identify other potential drivers of microbial community structure in cockroach guts, we determined the intestinal physicochemical parameters pH, redox potential, and oxygen and hydrogen partial pressure. Surprisingly, the localization of intestinal hydrogen accumulation in the crop of two cockroach species differed from that in the posterior midgut observed previously for omnivorous species. Intestinal pH, in addition to other, yet unidentified factors, was a strong determinant of bacterial community structure, posing a strong selection pressure particularly in the hindgut compartment. For a better understanding of the digestion of lignocellulose by cockroaches in nature, I fed two cockroach species on oak leaf litter, and determined the degradation efficiency and metabolization rates of lignocellulosic fractions and carbohydrate monomers through controlled mass balances (chapter 5). I found that xylan rather than cellulose was degraded in the gut, suggesting that litter-feeding cockroaches preferentially degrade the easily solubilizable diet fractions like hemicelluloses

Methanol oxidation by temperate soils and environmental determinants of associated methylotrophs

The role of soil methylotrophs in methanol exchange with the atmosphere has been widely overlooked. Methanol can be derived from plant polymers and be consumed by soil microbial communities. In the current study, methanol-utilizing methylotrophs of 14 aerated soils were examined to resolve their comparative diversities and capacities to utilize ambient concentrations of methanol. Abundances of cultivable methylotrophs ranged from 10 ⁶-10 ⁸gsoilDW ⁻¹. Methanol dissimilation was measured based on conversion of supplemented 14C-methanol, and occurred at concentrations down to 0.002 μmol methanol gsoilDW ⁻¹. Tested soils exhibited specific affinities to methanol (a ⁰ s=0 ⁻¹) that were similar to those of other environments suggesting that methylotrophs with similar affinities were present. Two deep-branching alphaproteobacterial genotypes of mch responded to the addition of ambient concentrations of methanol (≤0.6 μmol methanol gsoilDW ⁻¹) in one of these soils. Methylotroph community structures were assessed by amplicon pyrosequencing of genes of mono carbon metabolism (mxaF, mch and fae). Alphaproteobacteria-affiliated genotypes were predominant in all investigated soils, and the occurrence of novel genotypes indicated a hitherto unveiled diversity of methylotrophs. Correlations between vegetation type, soil pH and methylotroph community structure suggested that plant-methylotroph interactions were determinative for soil methylotrophs