BY

MARYAM IDRIS MUSA (20142926)

Introduction

Microbial diagnostic method

The use of skin bacteria and bactericidal activity to estimate

immune responsiveness

The total quantity of microorganisms on an area of skin

The number of haemolytic strains of microorganisms on the

skin

Presence of E coli in the mouth

The use of microecosystem response to indicate human

health

The estimation of the health and normal functioning of LSS

and its links

Eukaryotic/Prokaryotic Ratio

Conclusion

Life support systems are man made closed ecological systems, with different degree of complexity and closure. These include spacecraft and space stations (orbital vehicles or habitats, Mars or Moon stations)

LSS operating for prolonged periods, as well as submarines representing a kind of simulated environment with similarities to the natural environment maintained artificially, can be considered as “testbeds” for research on micro ecological dynamics, function and risk

Microorganisms are considered the most suitable indicators of a system’s health and its component links.

Microbial monitoring is critical to crew safety in long-duration space habitation and the sustained operation of life support systems on space transit vehicles and space stations.

Classically, microbial identification is based on microscopy of specimens and culturing on solid media.

Examination and insights into the dynamics of microorganisms as indicators of the health of closed systems require new developments and modifications to techniques that are presently used to measure microbial activity and their numbers.

For remote locations such as the space stations or comparable environments on Earth, rapid and easy to use methods that can be used on-site without the need for specialist expertise are invaluable for the detection and quantification of microbes.

For the use on-site, in particular on board of a spacecraft, microbial detection methods are preferred that take up as little volume and weight as possible during storage and transport due to high transportation costs and limited room for storage.

In addition, the methods should be safe to perform and the use of toxic chemicals and materials should be minimised.

Estimation of immune status of macroorganisms gives a more comprehensive indication of its health. Microbial resistance of the macroorganism can be estimated by the following parameters:

1. The total quantity of microorganisms on an area of skin.

2. Bactericidal activity of the skin

3. The number of haemolytic strains of microorganisms on the skin.

4. Presence of E. coli in the mouth.

To study skin microflora, a technique of inoculating the nutrient medium has been proposed. In this method, selective nutrient medium is applied to the slide plate; the plate is pressed against the surface of the skin and then Incubated in a thermostat

A healthy person has from five to eight microbial cells on a square centimetre of skin surface. The typical number of deep skin microflora is 8–12 cells/cm2

When immune responsiveness of the organism is disturbed, the number of microorganisms on the skin increases

The main indicator of inhibited immune responsiveness is lowered bacterial activity of the skin.

Bacterial activity can be estimated by applying a specific dose of a test microbe( E. coli) to a portion of the skin. A selective nutrient is then applied some minutes later

If bactericidal activity is high (a healthy person), the test microbe will fail to grow and dies. When there is a decrease in immune responsiveness, the test microbe will grow.

Presence of E coli in the mouth

The proportion of haemolytic strains gives an indication of their pathogenicity. Not more than 10% of haemolytic strains are found in a healthy person

Every location in the internal volume of an LSS can be mapped in terms of its normal state and deviations from the norm. This is one of the tasks facing those developing LSS and is particularly true of air samples, water samples, (potable and utility) and any surface within the LSS, including living macro organisms and those of the human occupants. As to potable water and the air in living compartments, they must meet the requirements of practical hygiene. The producer link in a biological LSS carries the main load, generating oxygen and biomass for other links of the system. Fortunately, these parameters are closely related to one another, and any increase in biomass can be measured directly by measuring the release of oxygen. This is a well developed technology.

Additional information on the health of this link can be obtained by examining the status of the algal reactor when it is part of the biological LSS

The E/P ratio is useful in assessing the algal reactor, since the slightest decrease in the growth of eukaryotic algae causes a concomitant increase in the number of prokaryotic bacteria. Real-time monitoring can be performed by measuring the ratio between green pigments and yellow ones

Use of adhesive sheet: This has several improvements over swab-based methods, including a simplified procedure, no water requirement for sample collection, and improved ease of transport and storage. The ability of the adhesive sheet to collect microbes from a metal plate and laptop palm rest (plastic, rough surface) was found to be equivalent to that of the swab.

This is a handheld device that enable crew to perform complex laboratory tests on a thumb-sized cartridge with a press of a button. It detects the presence of biological molecules found in the cell walls of bacteria and fungi. These molecules include:

i) Endotoxin also known as lipopolysaccharide LPS),

ii) ii) β-1, 3-glucan and

iii) lipoteichoic acid/peptidoglycan

With this method, Gram-negative bacteria stain pink and Gram-positive bacteria stain purple, and are related to structure of their cell walls

It has limitation in the in ability to differenciate dead from living cells.

Flight instrument and disposables for LOCAD-PTS

Sample being loaded into LOCAD-PTS

The technology utilizing gold nanoparticles for microbial monitoring is being investigations by space NASA. This is because of several unique properties of gold nanoparticles e.g. high stability, low toxicity, and photonic properties, that support their use in biodetection applications for crewed habitats in space.

gold nanoparticles functionalized by the conjugation of a ligand such as antibody can serve as chromogenic biosensors in which binding of the target to the ligand results in the agglomeration of nanoparticles and a red to purple shift.

Currently researchers are developing a biodetection system to detect S. aureus. Gold nanoparticles have been modified by the covalent attachment of an antibody that has a high binding affinity for a protein on the cell wall of S. aureus.

Data from preliminary testing of the gold nanoparticle biodetection system has shown that S. aureus could be detected in a sample in as quickly as 10min.

In order to be considered for flight evaluation, the technology must meet multiple design criteria:

1. Use quantitative or semi-quantitative PCR technology with multiplexing abilities;

2. Have a low limit of detection (≤ 400 cells sample−1 in a 100 μL sample volume);

3. Use reagents that are shelf-stable at room temperature for a minimum of six months;

4. Provide a rapid assessment of the microbial environment on the ISS;

5. Expand monitoring of microorganisms beyond current means;

6. Reduce the frequency of sampling events; 7. Allow for crew autonomy during sample analysis;

and 8. Have the ability to function in a microgravity

environment

The results of the experiments to date conducted in closed ecological systems and in spaceflight conditions argue for the ecological method of microflora control, i.e., for controlling the composition and numbers of microflora by maintaining proper environmental conditions. The alternative method – the establishment of sterile barriers between ecosystem links – is difficult to realize technically in a life support system with size and energy constraints. Sterile barriers may also be more dangerous than an ecological balance: if the barrier is broken by accident, which can hardly be avoided, the microflora, which has been developing in isolation until this moment, can change quickly and profoundly.

microorganisms, acting in LSS into three groups: useful, neutral and harmful. The tasks for human beings for optimal coexistence with micro habitants are simple yet challenging: (a) to increase the activity of useful forms, (b) decrease the activity of harmful forms, and (c) not allow the neutral forms to become harmful and even to help them to play a positive role in the overall engineered ecosystem