Table 1.

Structural preservation of Bacillus subtilis spores after microwave-assisted chemical fixation

No.	Fixation parameters	Microwave parameters	Round [%]	Condensed [%]	n
1.1	24 h, RTa	–	74	26	54
1.2	10′, RT	–	0	100	51
1.3	5′, RT/5′, 37°, MW	2′, RT→37°/3′, 37°	35	65	54
1.4	10′, RT/5′, 37°, MW	2′, RT→37°/3′, 37°	8	92	53
2.1	24 h, RTa	–	59	41	56
2.2	10′, 37°, MW	2′, RT→37°/8′, 37°	44	56	66
2.3	5′, RT/10′, 37°, MW	2′, RT→37°/8′, 37°	40	60	63
2.4	5′, RT/5′, 37°, MW	2′, RT→37°/3′, 37°, 100%	19	81	59
3.1	> 12 h, RTa	–	83	17	60
3.2	15′, 37°, MW	2′, RT→37°/13′, 37°	42	58	59
3.3	5′, RT/10′, 37°, MW/5′, RT/5′, 37°, MW	2′, RT→37°/8′, or 3′, 37°	16	84	61
3.4	5′, RT/5′, 37–50°, MW	2′, RT→37°/3′, 37→50°	79	21	62
4.1	24 h, RTa	–	34	66	58
4.2	5′, RT/10′, 37–50°, MW	2′, RT→37°/2′, 37°→50°/6′, 50°	81	19	59
4.3	5′, RT/10′, 50–60°, MW	2′, RT→37°/2′, 37°→50°/4′, 50°/2′, 50°→60°	85b	15	60
4.4	5′, RT/10′, 37–50°, MW	2′, RT→37°/5′, 37°/3′ 37°→50°	63	37	62
5.1	24 h, RTa	–	47	53	62
5.2	24 h, RTa	Depolymerization of PFA/2′ RT→70°, 100%/8′, 70°	51	49	61
5.3	5′, RT/10′, 37–50°, MW	2′, RT→37°/2′, 37°→50°/6′, 50°	93	7	59
5.4	5′, RT/5′, 37–50°, MW	2′, RT→37°/3′, 37°→50°	31	69	64

In five experiments (1–5) spore core preservation was evaluated. Round spore cores indicate a sufficient ultrastructural preservation.

MW = microwave.

RT = room temperature.

Microwave parameters: x′, RT→37° = increase from room temperature to 37 °C within x min; x′, 37° = holding at 37 °C for x min.

Microwave power was set to 15% except of No. 2.4 and 5.2.

^aFixation was done at room temperature (RT) for 1 h and the remaining time at 4 °C.

^bMembrane preservation was insufficient.