Phenotypic engineering of spores
The biological functionality of living microbial spores is modified using phenotypic engineering to endow the resulting modified spores with novel functionality that extends the usefulness of the spores for a variety of practical applications including, for example, sterility testing, the release of active compounds, and cell-based biosensing systems. An embodiment entails engineering Bacillus spores to acquire synthetic new functions that enable the modified spores to sense and rapidly transduce specific germination signals in their surroundings. The newly acquired functions allow the spores to perform, for example, as self-reporters of cellular viability, self-indicating components of cell-based biosensors, and in other analytical systems. Also disclosed are methods for testing adequate sterility of a system by using engineered spores.
1. A method of using engineered spores to test adequacy of a sterilization process for a system, comprising:
a) introducing the engineered spores into the system;
b) sterilizing the system, wherein the system with the engineered spores is subjected to the sterilization process;
c) exposing the engineered spores to a germinant for a predetermined germination period;
d) measuring fluorescence, wherein the fluorescence of the engineered spores is measured to obtain a fluorescence measurement; and
e) determining sterilization adequacy, such that:
if the fluorescence measurement is above a predetermined zero-baseline value, the sterilization process is determined to be inadequate, and
if the fluorescence measurement is equal to or less than the predetermined zero-baseline level, the sterilization process is determined to be adequate;
wherein the engineered spores each comprise:
a first spore; and
an at least partially hydrophobic compound, which is incorporated into the first spore;
wherein the at least partially hydrophobic compound is fluorogenic, such that the at least partially hydrophobic compound is configured to become fluorescent by hydrolysis;
wherein a sole fluorogenic compound in the engineered spores is the at least partially hydrophobic compound that is incorporated into the first spore in each of the engineered spores;
wherein the at least partially hydrophobic compound is present solely within the first spore in each of the engineered spores;
wherein the engineered spore is configured to be capable of germination; and
wherein the engineered spore is non-fluorescent;
wherein the engineered spore does not comprise a germinant;
such that the engineered spore is configured to become fluorescent upon germination.
2. The method of using engineered spores of claim 1 , wherein the sterilization process is dry heat sterilization, such that sterilizing the system comprises exposing the system with the engineered spores to dry heat in a temperature range of 140-160 degrees Celsius.
3. The method of using engineered spores of claim 1 , wherein the sterilization process is steam heat sterilization, such that sterilizing the system comprises exposing the system with the engineered spores to steam heat.
4. The method of using engineered spores of claim 1 , wherein the first spore is selected from the group consisting of bacteria, fungi, plants, and yeast.
5. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is an entirely hydrophobic compound.
6. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is an amphiphilic compound.
7. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is dipropionylfluorescein.
8. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is diacetyl fluorescein.
9. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is dibutyryl fluorescein.
10. The method of using engineered spores of claim 1 , wherein the at least partially hydrophobic compound is SYTO 9.
11. The method of using engineered spores of claim 1 , wherein the first spore is a spore of Geobacillus stearothermophilus.
12. The method of using engineered spores of claim 1 , wherein the first spore is a spore of Bacillus cereus.
13. The method of using engineered spores of claim 1 , wherein the first spore is a spore of Bacillus atrophaeus.
14. The method of using engineered spores of claim 1 , wherein the first spore is a spore of Bacillus megaterium.
15. A method of using engineered spores to test adequate sterility of a system, comprising sterilizing the system together with the engineered spores, subsequently incubating the engineered spores with a germinant, and finally measuring fluorescence of the engineered spores;
wherein the engineered spores each comprise:
a first spore; and
an at least partially hydrophobic compound, which is incorporated into the first spore;
wherein the at least partially hydrophobic compound is fluorogenic, such that the at least partially hydrophobic compound is configured to become fluorescent by hydrolysis;
wherein a sole fluorogenic compound in the engineered spores is the at least partially hydrophobic compound that is incorporated into the first spore in each of the engineered spores;
wherein the at least partially hydrophobic compound is present solely within the first spore in each of the engineered spores;
wherein the engineered spore is configured to be capable of germination; and
wherein the engineered spore is non-fluorescent;
wherein the engineered spore does not comprise a germinant;
such that the engineered spore is configured to become fluorescent upon germination.