Filtering by
- All Subjects: Microbiology
- Creators: Nickerson, Cheryl
![152348-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-09/152348-Thumbnail%20Image.png?versionId=aRU00I.Ltidzb53K4ePRFgwxTrhch4I9&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240605/us-west-2/s3/aws4_request&X-Amz-Date=20240605T144604Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=d27f65db441c5b4ce649feb45f9906371f73f7392d712cae835bdf3955a9f93d&itok=qBBPlJCy)
![151797-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-09/151797-Thumbnail%20Image.png?versionId=zw3p.Z4Q.C7_sW6ev5iMZkHfTz8zqiXl&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240530/us-west-2/s3/aws4_request&X-Amz-Date=20240530T153759Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=886c67ea7fab24a9534a9a6567f0fc454149f8b3f9e0f22a7696bfe51ffddb3e&itok=Iob8Bw3l)
![135647-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-05/135647-Thumbnail%20Image.png?versionId=84tYGsW3nx.Nu22UA4gnTgyye36sH2uY&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240530/us-west-2/s3/aws4_request&X-Amz-Date=20240530T153840Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=5fe6a267fd36559ddfe1f0124cf1500a7701ccd22ab2fcfec1695e12db78766e&itok=0TlkZ2uD)
![131560-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-07/131560-Thumbnail%20Image.png?versionId=BzR3yqttPk3ndaQRtELPrK_7bcJGigb.&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240614/us-west-2/s3/aws4_request&X-Amz-Date=20240614T103555Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=95909d58c15d07cb793bfc204d5199bc519700d5da7ba5ce3ec640db67fac2ba&itok=oeXEnqYC)
![133138-Thumbnail Image.png](/s3/files/styles/width_400/public/2021-05/133138-Thumbnail%20Image.png?itok=ZkFjGhmb)
![171573-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2022-12/171573-Thumbnail%20Image.png?versionId=Y7dDBQvZ.uWKOPkJn1LIqRUZZ7xGzaUw&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240615/us-west-2/s3/aws4_request&X-Amz-Date=20240615T094208Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=a872b2807385e5b5ab3a510fd5b9893c6fbf17948c356bb4b77c1d4db5cc45c7&itok=DeWNQbBb)
One of the identified health risk areas for human spaceflight is infectious disease, particularly involving environmental microorganisms already found on the International Space Station (ISS). In particular, bacteria belonging to the Burkholderia cepacia complex (Bcc) which can cause human disease in those who are immunocompromised, have been identified in the ISS water supply. This present study characterized the effect of spaceflight analog culture conditions on Bcc to certain physiological stresses (acid and thermal as well as intracellular survival in U927 human macrophage cells). The NASA-designed Rotating Wall Vessel (RWV) bioreactor was used as the spaceflight analogue culture system in these studies to grow Bcc bacterial cells under Low Shear Modeled Microgravity (LSMMG) conditions. Results show that LSMMG culture increased the resistance of Bcc to both acid and thermal stressors, but did not alter phagocytic uptake in 2-D monolayers of human monocytes.
![154002-Thumbnail Image.png](https://d1rbsgppyrdqq4.cloudfront.net/s3fs-public/styles/width_400/public/2021-08/154002-Thumbnail%20Image.png?versionId=E2jM31_buBwy585dbYQza4_lsF_6ouNx&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIASBVQ3ZQ42ZLA5CUJ/20240615/us-west-2/s3/aws4_request&X-Amz-Date=20240615T225618Z&X-Amz-SignedHeaders=host&X-Amz-Expires=120&X-Amz-Signature=da4fea765140ed035543db08bdc6270a54457169149c7c13715616fb0bcca693&itok=rqhE2BC9)
Antibacterial susceptibility testing reveals that hydrated clays containing pyrite and I-S are effective at killing (100%) of the model pathogens tested (E. coli and S. epidermidis) when pH (< 4.2) and Eh (> 450 mV) promote pyrite oxidation and mineral dissolution, releasing > 1 mM concentrations of Fe2+, Fe3+ and Al3+. However, certain oxidized clay zones containing no pyrite still inhibited bacterial growth. These clays buffered solutions to low pH (< 4.7) and oxidizing Eh (> 400 mV) conditions, releasing lower amounts (< 1 mM) of Fe and Al. The presence of carbonate in the clays eliminated antibacterial activity due to increases in pH, which lower pyrite oxidation and mineral dissolution rates.
The antibacterial mechanism of these natural clays was explored using metal toxicity and genetic assays, along with advanced bioimaging techniques. Antibacterial clays provide a continuous reservoir of Fe2+, Fe3+ and Al3+ that synergistically attack pathogens while generating hydrogen peroxide (H2O¬2). Results show that dissolved Fe2+ and Al3+ are adsorbed to bacterial envelopes, causing protein misfolding and oxidation in the outer membrane. Only Fe2+ is taken up by the cells, generating oxidative stress that damages DNA and proteins. Excess Fe2+ oxidizes inside the cell and precipitates Fe3+-oxides, marking the sites of hydroxyl radical (•OH) generation. Recognition of this novel geochemical antibacterial process should inform designs of new mineral based antibacterial agents and could provide a new economic industry for such clays.
The estimates of metal-ligand equilibrium constants at 25°C and 1 bar were made using multiple linear free energy relationships in accordance with the metal-coordinating properties of ligands such as denticity, identity of electron donor group, inductive effects and steric hindrance. Analogous relationships were made to estimated metal-ligand complexation entropy that facilitated calculation of equilibrium constants up to 125°C using the van’t Hoff equation. These estimates were made for over 250 ligands that include carboxylic acids, phenols, inorganic acids, amino acids, peptides and proteins.
The stability constants mentioned above were used to obtain metal speciation in several microbial growth media including past bioavailability studies and compositions listed on the DSMZ website. Speciation calculations were also carried out for several metals in blood plasma and cerebrospinal fluid that include metals present at over micromolar abundance (sodium, potassium, calcium, magnesium, iron, copper and zinc) and metals of therapeutic or toxic potential (like gallium, rhodium and bismuth). Metal speciation was found to be considerably dependent on pH and chelator concentration that can help in the selection of appropriate ligands for gallium & rhodium based anticancer drugs and zinc-based antidiabetics. It was found that methanobactin can considerably alter copper speciation and is therefore a suitable agent for the treatment of Wilson Disease. Additionally, bismuth neurotoxicity was attributed to the low transferrin concentration in cerebrospinal fluid and the predominance of aqueous bismuth trihydroxide. These results demonstrate that metal speciation calculations using thermodynamic modeling can be extremely useful for understanding metal bioavailability in microbes and human bodily fluids.