183: Survivors' experiences (3)

The questions were highly targeted, directly addressing the core logic and common pitfalls in the application of genetic engineering. Pang Bo quickly jotted down keywords on the provided draft paper, his mind racing as he reactivated professional knowledge that had been dormant for months but was already ingrained in his blood.

After a moment of contemplation, he looked up, his eyes regaining their confidence and focus:

"Teacher Wang, here is my answer:

First, for the first question, receptor bacteria selection: I would prioritize choosing E. coli as the receptor bacterium. The main reasons are: E. coli is the most classic and thoroughly studied model microorganism, with a clear genetic background, fast reproduction rate, low culture cost, high transformation efficiency, and a large number of verified mature expression vectors and operating toolkits (such as various inducible promoter vectors). It is very suitable as the initial receptor bacterium for feasibility verification and preliminary mass production in foreign protein expression projects like 'Extreme Environment Stress Resistance Protein'.

"For the second question, core critical operations:

The first step is 'directional cloning' of the foreign gene and vector: This step must use the same restriction endonuclease (or isoschizomers that produce compatible ends) to simultaneously cut the coding gene fragment of the 'Extreme Environment Stress Resistance Protein' and the expression vector containing a specific inducible promoter. This ensures that the target gene is inserted downstream of the promoter in the correct orientation and reading frame. This is the basis for ensuring that the target gene can be precisely regulated by the inducible promoter and correctly translated into an active protein. Otherwise, all subsequent work will be meaningless.

The second step is 'positive clone screening and verification' of the recombinant vector: After transforming E. coli with the ligation product, methods such as antibiotic screening (using the antibiotic resistance gene carried by the vector) and blue-white screening (if applicable) are needed to initially screen for colonies that may contain the recombinant plasmid. It is crucial to then confirm the correct size and orientation of the inserted fragment at the molecular level using techniques like colony PCR or plasmid restriction enzyme digestion. This is a key quality control step to avoid obtaining empty vectors or incorrect recombinants, which can greatly save time and effort in subsequent verification.

"For the third question, the reason for prioritizing promoter activity verification: Because the inducible promoter is the core component for achieving 'controllable expression' of the protein. If protein expression is directly detected and the result is negative, it's impossible to distinguish whether it's a fundamental construction failure (e.g., gene not ligated, ligated incorrectly, or broken) or if the construction itself was successful but induction conditions were not optimized or the protein was rapidly degraded after expression. However, promoter activity verification experiments (for example, ligating the promoter to a reporter gene like the GFP Gene, constructing a reporter vector, and observing if the reporter gene is expressed under induced conditions) can independently and directly confirm: first, that our constructed vector itself is successful; and second, that our chosen inducible promoter can be effectively induced and initiate downstream gene transcription in this experimental system. This is equivalent to eliminating the biggest variable, providing a clear direction and confidence for subsequent optimization of protein expression conditions. Therefore, this is a more efficient and logically rigorous initial verification strategy."

Pang Bo's answer was clear, well-organized, and highlighted key points. He not only answered "what" but also explained "why." Engineer Wang listened, and a look of approval gradually appeared on his originally serious face, as he nodded slightly from time to time.

"Good, your theoretical foundation is very solid." Engineer Wang affirmed, then posed a more in-depth application-oriented question: "So, if the initial construction is successful, but after induced expression, the target protein is found to exist mostly in inclusion bodies with very low activity, what aspects would you prioritize for optimization?"

Pang Bo thought for a moment, then answered fluently: "I would prioritize the following points: 1. Lowering the induction temperature, for example, from 37°C to 16-25°C, to slow down protein synthesis and promote correct folding; 2. Optimizing the inducer concentration and induction time to find the optimal window; 3. Changing the expression strain, such as using strains rich in molecular chaperones like Origami, which facilitate disulfide bond formation; 4. Considering co-expression with molecular chaperone proteins; 5. If the sequence allows, trying to change the expression vector or promoter system..."

"Excellent!" Engineer Wang's face broke into a satisfied smile, interrupting Pang Bo (who clearly didn't need to finish his entire answer), "Young man, your abilities and knowledge base are excellent, and your foundation is very solid. Tomorrow, you will report to my project team and start as a research assistant."

"Thank you, Teacher! Thank you, Teacher!" Pang Bo excitedly stood up, bowing repeatedly. The heavy stone in his heart finally dropped, and his joy was palpable. He knew that he had not only found a job but had also returned to his beloved field of research!

Special Talent Channel - Medical Assessment Room

Meanwhile, Professor Wang Kunlin was invited into another quiet assessment room. Inside sat two examiners, also dressed in white coats, with calm temperaments and similar ages to him—they were also advanced Engineers (professor-level) in clinical medicine who had been promoted through the system.

"Professor Wang, it's an honor to meet you, please have a seat." The two examiners were polite, not putting on airs despite being examiners. They ought to show considerable respect to a clinical expert with national-level projects and a Level 3 professorship.

"You two professors are too kind." Wang Kunlin sat down gracefully, neither humble nor arrogant.

"Professor Wang. Your qualifications are beyond doubt, so we'll skip the basic assessment. How about you give us a detailed introduction to the main research directions, innovations, and phased achievements of that national key R&D program project you previously led?" one examiner said with a smile.

"Alright." Wang Kunlin nodded and began to elaborate calmly. He started from the background and clinical significance of the project's establishment, delved into specific research designs, key technical routes adopted, disease models established, technical difficulties encountered and how they were overcome, and finally, the preliminary experimental data and promising conclusions... He spoke with clarity and depth, his logic rigorous, occasionally picking up a pen to write down key data and complex signal pathway diagrams on the whiteboard to illustrate his points.

The two examiners listened very attentively, occasionally asking one or two highly professional questions, which Wang Kunlin quickly understood and answered clearly.

After nearly forty minutes, Wang Kunlin paused, saying with a hint of regret: "...The major breakthroughs and subsequent in-depth mechanistic explorations were originally planned for the end of this year, but unfortunately, the apocalypse broke out, and all research was forced to stop."

The two examiners exchanged glances, both seeing recognition and regret in each other's eyes. "That's enough, Professor Wang," one examiner said. "Your academic level and clinical research mindset are beyond doubt. This is your appointment letter. Please report to the Resident Hospital Management Center with this. The person in charge there will arrange a corresponding department and position for you based on your professional direction, and provide funding and equipment for your research. We believe your research on pulmonary immune microenvironment regulation can quickly yield conclusions. The base greatly needs talent like you."

Wang Kunlin took the letter, stamped with the Red Alert Legion Human Resources Department's seal, with both hands, filled with emotion, and solemnly said: "Thank you! I will do my best."

...Pang Bo, who had been assigned talent housing, took the key and followed the signs to his new home—located in Block B, Building 56 of the residential area. He swiped his ID card, which had access control recorded on it, to open the door, and the sight that greeted him instantly made him forget all his fatigue.

This was a standard two-bedroom, one-living room, one-kitchen, one-bathroom suite, about 80 square meters in size. The rooms were bright and airy, with sunlight streaming through the clean glass windows onto the polished floor, making it feel especially bright and warm.

Basic furniture such as a bed, wardrobe, desk, sofa, and dining table and chairs were all available. Although the style was simple, everything was brand new. The kitchen also had basic stoves, cooking utensils, and a pristine white sink. The independent bathroom had a wet-dry separation, with a squat toilet, showerhead, and washbasin sparkling clean.

"This... this is so much better than the place I rented before the apocalypse!" Pang Bo excitedly walked back and forth between the two rooms, finally throwing himself onto the soft new bed with a comfortable sigh. "It's like a dream..."

He gazed at the white ceiling, his mind full of thoughts: "Tomorrow I can report to the base research center. I wonder what direction Teacher Wang's research mainly focuses on? Hopefully, it's related to gene editing or agricultural yield increase, which would suit the needs of the apocalypse..." Thinking about being able to work with his beloved experimental equipment again and dedicate himself to scientific research, he couldn't help but roll over in bed with joy.

Suddenly, a thought popped into his head: "Hey, I wonder if there are any young female assistant teachers or female researchers in the research center...? I hope there are some who are good-looking and have good personalities..." He thought about how he was already in his early thirties and still single because he had been focused on his studies and scientific research, and he couldn't help but feel a little hopeful. In his opinion, he was now considered a "senior talent" certified by the base, so finding a compatible partner shouldn't be too difficult, right? With this dual expectation for career and love, he smiled and drifted off to sleep.

On the other side, Nurse Li Li and three other young nurses who had also passed the assessment were assigned to the same standard housing unit. The room layout was identical to Pang Bo's, but the bedrooms had two single beds arranged side-by-side, with four of them sharing two rooms.

"Sisters! I've grabbed the bathroom to shower first!" Li Li cheered, rushing into the bathroom with her new towel and toiletries bag.

"Hey! Li Li, you're cheating! Wait for me!" A lively nurse named Xiao Wen, quick with her eyes and hands, playfully squeezed in before Li Li could lock the door. "It's such a waste of water to shower alone, let's save resources, together, together!"

"Ah! Get out!"

"No! I'll help you scrub your back!"

Immediately, the sound of splashing water and the playful shouts and laughter of the two girls filled the bathroom, full of youthful vitality.

The other two roommates couldn't help but laugh at the scene.

After a long while, all four girls had finished their hot showers, smelling of shower gel, and wearing comfortable pajamas, each collapsing onto their own beds.

"Oh my god... this is just too comfortable..." one girl sighed contentedly, rubbing her face against the soft, clean pillow. "It feels like being reborn..."

"Yeah... finally no more smell of sweat, foot odor, and despair mixed in the prefabricated house... I feel like the air is sweet now..."

"Sisters, after enjoying today, tomorrow we'll have to go to the hospital and work like oxen and horses..." Li Li said, though a smile played on her lips.

"Sigh, just thinking about all those nursing documents, three checks and seven pairs, and possible night shifts..." Xiao Wen feigned a wail.

No one knew who started complaining about the Nursing Department's rounds and regular skill assessments, but suddenly, the four girls shouted in unison: "Resist the Nursing Department!!!"

After shouting, they themselves couldn't help but burst into giggles.

This joking shout carried a small complaint about past professional pressures, but more than that, it held joy and anticipation for a new beginning and a stable life. They knew that even if the work was hard, at least they had a true home again.

Similar heartwarming scenes were unfolding in thousands of newly settled families in the base. Under the lights, there were the refreshed faces of survivors after cleaning up, the laughter of children running and playing in the rooms, the reassuring smiles exchanged between couples, and the quiet satisfaction of single residents enjoying a moment of peace.

The spark of human hope had not been extinguished; under the protection of this steel city, it ignited into a warm and bright flame.